Implemented getTotalPriceMessage() function that return a message with the total cost that the client needs to pay.

Author: ddryzhov

src/main/kotlin/mate/academy/BuyProducts.kt

@@ -1,5 +1,5 @@
 package mate.academy
 
 fun getTotalPriceMessage(client: String, price: Int, quantity: Int): String {
-    return ""
+    return "$client has to pay $${quantity * price} per $quantity products"
 }