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

[Q]: Sentence: 'a couple of buildings that has a bus out front'. Find frequency of the letter 'a'
[A]: 4


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


[Q]: Sentence: 'woman getting ready to enter an empty subway car'. Find frequency of the letter 'a'
[A]:
5