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

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


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


[Q]: Sentence: 'students sitting in a hallway using their laptops'. Find frequency of the letter 'l'
[A]:
3