In this task, you need to count the number of times the given letter appears in the given sentence.

Input: Consider Input: Sentence: 'a bunch of green bananas is hanging on a tree'. Find frequency of the letter 'n'

Output: 7

Input: Consider Input: Sentence: 'a truck with a camper sits parked in some vegetation'. Find frequency of the letter 's'

Output: 3

Input: Consider Input: Sentence: 'some fruit in case and wrapping on a concrete'. Find frequency of the letter 'a'
Output: 4