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

Sentence: 'two boys are doing skateboard jumps in the street'. Find frequency of the letter 's'
4

Sentence: 'a bunch of green bananas is hanging on a tree'. Find frequency of the letter 'n'
7

Sentence: 'a group of police officers standing near a bed of flowers'. Find frequency of the letter 'p'
2