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

[EX Q]: Sentence: 'older man getting ready to swing his bat at a ball on a stand in front of a group of viewers'. Find frequency of the letter 'n'
[EX A]: 7

[EX Q]: Sentence: 'a batter, catcher and umpire waiting for the pitch and a major league baseball game'. Find frequency of the letter 'c'
[EX A]: 3

[EX Q]: Sentence: 'there is a short train moving down the tracks'. Find frequency of the letter 'a'
[EX A]:
3