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

Sentence: 'a car accident has slowed traffic as a clean up crew works'. Find frequency of the letter 'f'
2

Sentence: 'some cubbies with towels in a blue bathroom'. Find frequency of the letter 'l'
2

Sentence: 'a baseball player sliding into a base on a field'. Find frequency of the letter 'a'

7