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

Sentence: 'a large group of motorcycles parked along a street'. Find frequency of the letter 'a'
5

Sentence: 'a passenger train that is going over a bridge'. Find frequency of the letter 't'
3

Sentence: 'a smiling woman with red hair showing a bowl of greens'. Find frequency of the letter 'i'

5