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

Sentence: 'a girl hitting a tennis ball on a court'. Find frequency of the letter 'l'
3

Sentence: 'wooden and black bench on the side of the road'. Find frequency of the letter 'a'
3

Sentence: 'a realistic painting of two zebras huddled in brown grass'. Find frequency of the letter 'e'

3