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

Sentence: 'a man holding a baseball bat an playing baseball'. Find frequency of the letter 'l'
6

Sentence: 'a guy riding a bike close to a car in the street'. Find frequency of the letter 'i'
4

Sentence: 'an image of a man that is playing soccer'. Find frequency of the letter 'i'
3