c++

2.1 Question 11/20 points) Write a program that reads a lower-case letter in Letter, and prints a shape of an isosceles triangle. The first line of the triangle should have the letter a, the second line of the triangle should have the letter b, the third line of the triangle should have the letter c, the last line of the triangle should have the letter in Letter. In addition, the casing of the letters should alternate between lines. That is, in the first line, the 'a' should be lower case. In the second line, all 'b's should be upper case. In the third line, all the 'c's should be lower case, etc. Your program should interact with the user exactly as it shows in the following two executions: Execution example 1: Please enter a lower-case letter: e a BBB ccccc DDDDDDD eeeeeeeee Execution example 2: Please enter a lower-case letter: d a BBB CCCCC DDDDDDD