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

[Q]: Sentence: 'surfboard being displayed in stor window with clothes behind it'. Find frequency of the letter 't'
[A]: 4

[Q]: Sentence: 'a bus is driving on the street behind some cars'. Find frequency of the letter 'a'
[A]: 2

[Q]: Sentence: 'a picture of a man with a mustache holding a racket'. Find frequency of the letter 'a'
[A]:
7