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

Sentence: 'a woman cross country skiing in a competition'. Find frequency of the letter 's'
3

Sentence: 'a room with a big screen television and a couch'. Find frequency of the letter 'h'
2

Sentence: 'a large round mirror sitting up on an orange pole'. Find frequency of the letter 'e'
3