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

Sentence: 'people playing wii bowling in a modern library'. Find frequency of the letter 'o'
3

Sentence: 'an elephant with broken tusks stands in front of a hill and boulders'. Find frequency of the letter 'n'
7

Sentence: 'the row of motorcycles is displaying the flags'. Find frequency of the letter 'e'

3