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

[EX Q]: Sentence: 'a bunch of broken down trains sit in a yard'. Find frequency of the letter 'n'
[EX A]: 5

[EX Q]: Sentence: 'a bus is driving on the street behind some cars'. Find frequency of the letter 'a'
[EX A]: 2

[EX Q]: Sentence: 'small clean white kitchen area with dark appliances'. Find frequency of the letter 'l'
[EX A]:
4