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 girl that has a kite in the air'. Find frequency of the letter 'r'
2

Sentence: 'two pairs of animals grazing in the pasture'. Find frequency of the letter 's'

3