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

[EX Q]: Sentence: 'a man standing on a tennis court holding a racquet'. Find frequency of the letter 's'
[EX A]: 2

[EX Q]: Sentence: 'two men are playing a video game as another sits watching'. Find frequency of the letter 'a'
[EX A]: 7

[EX Q]: Sentence: 'a large group of people skateboarding down a city street together with no cars on the street'. Find frequency of the letter 'e'
[EX A]:
11