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

[EX Q]: Sentence: 'a girl laying on a bed posing for a picture'. Find frequency of the letter 'i'
[EX A]: 4

[EX Q]: Sentence: 'a man makes some cock tales at a desk'. Find frequency of the letter 'k'
[EX A]: 3

[EX Q]: Sentence: 'a baseball player sliding to the base to avoid being tagged'. Find frequency of the letter 'a'
[EX A]:
7