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

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

[EX Q]: Sentence: 'the red train cabin is marked number 2'. Find frequency of the letter 'i'
[EX A]:
3