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

Ex Input:
Sentence: 'two laptop computers sitting on top of a white table'. Find frequency of the letter 'f'

Ex Output:
1

Ex Input:
Sentence: 'a man skating down a stair rail in front of a bunch of people'. Find frequency of the letter 'o'

Ex Output:
5

Ex Input:
Sentence: 'two men in black wet suits beside a white surfboard'. Find frequency of the letter 'e'

Ex Output:
5