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

Q: Sentence: 'a young boy bouncing a tennis ball on a tennis racquet'. Find frequency of the letter 'a'

A: 5
****
Q: Sentence: 'a flock of sheep grazing in a park'. Find frequency of the letter 'f'

A: 2
****
Q: Sentence: 'a couple of people riding on the back of a boat'. Find frequency of the letter 'o'

A:
6
****