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

Sentence: 'a large grass pasture land with sheep grazing on grass'. Find frequency of the letter 'a'
7

Sentence: 'girls posing of a picture one holding a tennis racket the other wearing a crown'. Find frequency of the letter 'g'
4

Sentence: 'a pitcher draws back to throw a baseball'. Find frequency of the letter 'b'

3