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

Sentence: 'a blue fire hydrant painted on the bottom of it'. Find frequency of the letter 'h'
2

Sentence: 'this yellow fire hydrant sits in a grass field'. Find frequency of the letter 'i'
5

Sentence: 'a group of four people riding skis while holding ski poles'. Find frequency of the letter 'e'

4