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

Sentence: 'a plastic container next to a toilet on a wooden box'. Find frequency of the letter 'i'
3

Sentence: 'a man skating down a stair rail in front of a bunch of people'. Find frequency of the letter 'o'
5

Sentence: 'there are people walking near trucks with satellite dishes'. Find frequency of the letter 'e'

9