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

[EX Q]: Sentence: 'a couple of girls are hanging out at a restaurant'. Find frequency of the letter 'l'
[EX A]: 2

[EX Q]: Sentence: 'three men in military suits are sitting on a bench,'. Find frequency of the letter 'a'
[EX A]: 3

[EX Q]: Sentence: 'the man is jumping on a ramp on his skateboard'. Find frequency of the letter 'm'
[EX A]:
3