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

Sentence: 'a woman in a messy kitchen with a child'. Find frequency of the letter 'a'
4

Sentence: 'a man sitting on a motorcycle near two other men'. Find frequency of the letter 'r'
3

Sentence: 'a pizza sitting in an oven, in a blurry picture'. Find frequency of the letter 'a'

4