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

Sentence: 'a person trying to flip a skateboard in a garage'. Find frequency of the letter 'a'
7

Sentence: 'a person riding a skate board on a city street'. Find frequency of the letter 'a'
5

Sentence: 'a lone zebra stands between some trees with a zoo sign in the background'. Find frequency of the letter 'o'

5