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

[EX Q]: Sentence: 'a player swings his bat at a baseball game'. Find frequency of the letter 'p'
[EX A]: 1

[EX Q]: Sentence: 'this yellow fire hydrant sits in a grass field'. Find frequency of the letter 'i'
[EX A]: 5

[EX Q]: Sentence: 'three places at the long table are set for a meal'. Find frequency of the letter 'l'
[EX A]:
4