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

Sentence: 'many white birds flying above a river that flows in front of a forest'. Find frequency of the letter 'a'
5

Sentence: 'a couple of men standing inside of a liquor store'. Find frequency of the letter 'p'
1

Sentence: 'a red and white car parked on beach with a flag'. Find frequency of the letter 'h'

3