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

Sentence: 'a line of people on motorcycles on the road'. Find frequency of the letter 'e'
5

Sentence: 'a guy surfs a wave with his surfboard'. Find frequency of the letter 's'
4

Sentence: 'a cow figure standing next to a large clock'. Find frequency of the letter 'x'

1