A=220, April =220- 1=2 19, May =2 19 times 2- 1=437, and June =12 * 220-/kloc-.
Check calculation: the total amount is equal to 15a- 15=3285, and three months add up to 3285.
So the calculation is correct.
It's hard to answer questions, so plagiarism is declined. If you are satisfied, please give a good comment.
The first answer above is obviously wrong.