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

Sentence: 'a fluffy white car looking in a mirror'. Find frequency of the letter 'k'
1

Sentence: 'a sailboat is floating near the rocky shore of a beach'. Find frequency of the letter 'o'
5

Sentence: 'two men are driving motorbikes with small boys'. Find frequency of the letter 's'

3