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

Sentence: 'a person is riding in a cart pulled by a horse'. Find frequency of the letter 'a'
4

Sentence: 'two giraffes, one standing and one laying down'. Find frequency of the letter 'g'
3

Sentence: 'the boy swings the bat as he plays in the little league game'. Find frequency of the letter 'e'

8