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

[EX Q]: Sentence: 'a person dressed all in black snowboarding down a slope'. Find frequency of the letter 'e'
[EX A]: 4

[EX Q]: Sentence: 'a police officer who is riding on a horse'. Find frequency of the letter 'p'
[EX A]: 1

[EX Q]: Sentence: 'horses are pulling a trailer with barrels on it'. Find frequency of the letter 't'
[EX A]:
3