diff --git a/for-loops.ipynb b/for-loops.ipynb
index d8dc735..55cb1d3 100644
--- a/for-loops.ipynb
+++ b/for-loops.ipynb
@@ -22,9 +22,19 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 3,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "odysseus\n",
+      "neoptolemus\n",
+      "philoctetes\n"
+     ]
+    }
+   ],
    "source": [
     "cast = [\"odysseus\", \"neoptolemus\", \"philoctetes\"]\n",
     "\n",
@@ -47,7 +57,7 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 4,
    "metadata": {},
    "outputs": [],
    "source": [
@@ -63,9 +73,20 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 5,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "odysseus\n",
+      "neoptolemus\n",
+      "philoctetes\n",
+      "And now the loop is done!\n"
+     ]
+    }
+   ],
    "source": [
     "cast = [\"odysseus\", \"neoptolemus\", \"philoctetes\"]\n",
     "\n",
@@ -86,9 +107,18 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 6,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "ename": "IndentationError",
+     "evalue": "expected an indented block after 'for' statement on line 3 (3799840020.py, line 4)",
+     "output_type": "error",
+     "traceback": [
+      "\u001b[0;36m  Cell \u001b[0;32mIn[6], line 4\u001b[0;36m\u001b[0m\n\u001b[0;31m    print(character)\u001b[0m\n\u001b[0m    ^\u001b[0m\n\u001b[0;31mIndentationError\u001b[0m\u001b[0;31m:\u001b[0m expected an indented block after 'for' statement on line 3\n"
+     ]
+    }
+   ],
    "source": [
     "cast = [\"odysseus\", \"neoptolemus\", \"philoctetes\"]\n",
     "\n",
@@ -278,9 +308,21 @@
   },
   {
    "cell_type": "code",
-   "execution_count": null,
+   "execution_count": 11,
    "metadata": {},
-   "outputs": [],
+   "outputs": [
+    {
+     "ename": "TypeError",
+     "evalue": "'tuple' object does not support item assignment",
+     "output_type": "error",
+     "traceback": [
+      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
+      "\u001b[0;31mTypeError\u001b[0m                                 Traceback (most recent call last)",
+      "Cell \u001b[0;32mIn[11], line 3\u001b[0m\n\u001b[1;32m      1\u001b[0m my_tuple \u001b[38;5;241m=\u001b[39m (\u001b[38;5;241m1\u001b[39m, \u001b[38;5;241m2\u001b[39m, \u001b[38;5;241m3\u001b[39m)\n\u001b[0;32m----> 3\u001b[0m \u001b[43mmy_tuple\u001b[49m\u001b[43m[\u001b[49m\u001b[38;5;241;43m1\u001b[39;49m\u001b[43m]\u001b[49m \u001b[38;5;241m=\u001b[39m \u001b[38;5;241m5\u001b[39m\n",
+      "\u001b[0;31mTypeError\u001b[0m: 'tuple' object does not support item assignment"
+     ]
+    }
+   ],
    "source": [
     "my_tuple = (1, 2, 3)\n",
     "\n",
@@ -304,11 +346,118 @@
     "\n",
     "Matthes 2023, p. 67, Exercise 4-13."
    ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "4-13. Buffet: A buffet-style restaurant offers only five basic foods. Think of five\n",
+    "simple foods, and store them in a tuple.\n"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 14,
+   "metadata": {},
+   "outputs": [],
+   "source": [
+    "menu = (\"spring roll\", \"ramen\", \"curry\", \"rice\", \"steak\")"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "- Use a for loop to print each food the restaurant offers"
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 15,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "spring roll\n",
+      "ramen\n",
+      "curry\n",
+      "rice\n",
+      "steak\n"
+     ]
+    }
+   ],
+   "source": [
+    "for food in menu:\n",
+    "    print(food)"
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "- Try to modify one of the items, and make sure that Python rejects the\n",
+    "change."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 16,
+   "metadata": {},
+   "outputs": [
+    {
+     "ename": "TypeError",
+     "evalue": "'tuple' object does not support item assignment",
+     "output_type": "error",
+     "traceback": [
+      "\u001b[0;31m---------------------------------------------------------------------------\u001b[0m",
+      "\u001b[0;31mTypeError\u001b[0m                                 Traceback (most recent call last)",
+      "Cell \u001b[0;32mIn[16], line 1\u001b[0m\n\u001b[0;32m----> 1\u001b[0m \u001b[43mmenu\u001b[49m\u001b[43m[\u001b[49m\u001b[38;5;241;43m1\u001b[39;49m\u001b[43m]\u001b[49m \u001b[38;5;241m=\u001b[39m \u001b[38;5;124m\"\u001b[39m\u001b[38;5;124mnone\u001b[39m\u001b[38;5;124m\"\u001b[39m\n",
+      "\u001b[0;31mTypeError\u001b[0m: 'tuple' object does not support item assignment"
+     ]
+    }
+   ],
+   "source": [
+    "menu[1] = \"none\""
+   ]
+  },
+  {
+   "cell_type": "markdown",
+   "metadata": {},
+   "source": [
+    "- The restaurant changes its menu, replacing two of the items with different\n",
+    "foods. Add a line that rewrites the tuple, and then use a for loop to print\n",
+    "each of the items on the revised menu."
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": 17,
+   "metadata": {},
+   "outputs": [
+    {
+     "name": "stdout",
+     "output_type": "stream",
+     "text": [
+      "bread\n",
+      "ramen\n",
+      "braised pork\n",
+      "rice\n",
+      "steak\n"
+     ]
+    }
+   ],
+   "source": [
+    "menu = (\"bread\", \"ramen\", \"braised pork\", \"rice\", \"steak\")\n",
+    "for food in menu:\n",
+    "    print(food)"
+   ]
   }
  ],
  "metadata": {
   "kernelspec": {
-   "display_name": ".venv",
+   "display_name": "Python 3",
    "language": "python",
    "name": "python3"
   },
@@ -322,7 +471,7 @@
    "name": "python",
    "nbconvert_exporter": "python",
    "pygments_lexer": "ipython3",
-   "version": "3.12.7"
+   "version": "3.12.1"
   }
  },
  "nbformat": 4,