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

[EX Q]: Sentence: 'a person riding a skate board on a city street'. Find frequency of the letter 'a'
[EX A]: 5

[EX Q]: Sentence: 'a man swinging a bat while playing baseball'. Find frequency of the letter 'm'
[EX A]: 1

[EX Q]: Sentence: 'a red-haired woman is gesturing toward a red double-decker bus in europe'. Find frequency of the letter 'e'
[EX A]:
9