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

[Q]: Sentence: 'a small boat and a large boat on a river near a city'. Find frequency of the letter 'a'
[A]: 10


[Q]: Sentence: 'a woman is looking at sheep off in a field'. Find frequency of the letter 'm'
[A]: 1


[Q]: Sentence: 'a phone wearing glasses on a brown table'. Find frequency of the letter 'n'
[A]:
4