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

[Q]: Sentence: 'a man that is on his cell phone'. Find frequency of the letter 's'
[A]: 2


[Q]: Sentence: 'a street at night with trees and streetlights on'. Find frequency of the letter 't'
[A]: 9


[Q]: Sentence: 'a shelf with many pairs of shoes and a skateboard leaning against the wall'. Find frequency of the letter 'n'
[A]:
5