cash register on ruby

The Cash Register Here are the prices for five items: A) 0.50 or 3 for $1.00 B) 1.25 C) 0.75 or 4 for $2.50 D) 1.00 E) 0.69 Write a program that will allow a person to enter the letters A, B, C, D, or E as many times as they like. If you hit any letter other than these five, the screen will show the total cost of the purchase. The program should accept either upper case or lower case for the five letters as valid.