$1.$ Financial application: calculate tip

Write a program named $$LastNameTip$$ that reads the subtotal and the gratuity rate and

then computes the gratuity and total. For example, if the user enters $10$ for the subtotal, and $15\%$ for the gratuity rate, the program displays $$1\mathrm{.}50$ as gratuity and $11\mathrm{.}50$ as total. The program should let the user know if they have entered a subtotal or a gratuity rate that is negative and if so$,$ the program should end without doing any math.

Here is a sample run; the bold represents the input from the user:

Enter the subtotal: $10$

Gratuity rate in $\%$: $15$

The Gratuity is $$1\mathrm{.}50$ and the total is $$11\mathrm{.}50$