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

Ex Input:
Sentence: 'a woman swinging a tennis racquet towards a tennis ball'. Find frequency of the letter 'e'

Ex Output:
3


Ex Input:
Sentence: 'a street scene looking at the back of the stop sign'. Find frequency of the letter 't'

Ex Output:
6


Ex Input:
Sentence: 'a kitchen with a refrigerator and a microwave'. Find frequency of the letter 'a'

Ex Output:

6