Currency symbol system dependent

[Elyasin]

Initially the activity layout displays a currency symbol $ though once the button is pushed it displays the symbol of my region, the € symbol.

It seems system dependent to me. The test case may need to be adapted to make it run successfully.

[gshadows]

To fix this for this project purposes only, change NumberFormat.getCurrencyInstance() to the NumberFormat.getCurrencyInstance(Locale.US) in two places: OrderActivity.displayCost() and OrderSummaryActivity.displayOrderSummary().