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

Ex Input:
Sentence: 'three men are in a kitchen cooking and cutting through a dish'. Find frequency of the letter 'a'

Ex Output:
4

Ex Input:
Sentence: 'a tennis player that is running to get the tennis ball'. Find frequency of the letter 't'

Ex Output:
7

Ex Input:
Sentence: 'a man is in position to play on a tennis court'. Find frequency of the letter 'n'

Ex Output:
6