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

Sentence: 'a girl sits on a surfboard and smiles'. Find frequency of the letter 'i'
3

Sentence: 'three young people goofing around; one of the guys has a football, the girl has a teddy bear'. Find frequency of the letter 'd'
3

Sentence: 'a picture of two skis and two poles'. Find frequency of the letter 's'

3