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: 'a close up of a bird on the outside window sill'. Find frequency of the letter 'c'
[EX A]: 1

[EX Q]: Sentence: 'the bicyclist is doing a trick on his black bike'. Find frequency of the letter 'i'
[EX A]:
7