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

Sentence: 'a man in a black wet suit rides an orange surfboard on the water'. Find frequency of the letter 'o'
3

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

Sentence: 'baseball player running on top of a baseball field'. Find frequency of the letter 'd'

1