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

[Q]: Sentence: 'the snowboarder wearing a dark helmet sprays snow into the air'. Find frequency of the letter 'w'
[A]: 3

[Q]: Sentence: 'a street scene looking at the back of the stop sign'. Find frequency of the letter 't'
[A]: 6

[Q]: Sentence: 'there are many cars on the road by the tall buildings'. Find frequency of the letter 'a'
[A]:
5