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

Sentence: 'a train is sitting at a train station'. Find frequency of the letter 'r'
2

Sentence: 'a cooked pizza on a silver platter with another in the background'. Find frequency of the letter 'e'
5

Sentence: 'three giraffe and two zebras are grazing in the grass together'. Find frequency of the letter 'e'

8