Update price in view model

app/src/main/java/com/example/cupcake/model/OrderViewModel.kt

@@ -7,6 +7,8 @@ import java.text.SimpleDateFormat
 import java.util.Calendar
 import java.util.Locale
 
+private const val PRICE_PER_CUPCAKE = 2.00
+
 class OrderViewModel : ViewModel() {
     private val _quantity = MutableLiveData<Int>()
     val quantity: LiveData<Int> = _quantity
@@ -26,6 +28,10 @@ class OrderViewModel : ViewModel() {
         resetOrder()
     }
 
+    private fun updatePrice() {
+        _price.value = (quantity.value ?: 0) * PRICE_PER_CUPCAKE
+    }
+
     private fun getPickupOptions(): List<String> {
         val options = mutableListOf<String>()
         val formatter = SimpleDateFormat("E MMM d", Locale.getDefault())
@@ -47,6 +53,7 @@ class OrderViewModel : ViewModel() {
 
     fun setQuantity(numberCupcakes: Int) {
         _quantity.value = numberCupcakes
+        updatePrice()
     }
 
     fun setFlavor(desiredFlavor: String) {