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

[Q]: Sentence: 'a glass a rope and a pair of scissors'. Find frequency of the letter 's'
[A]: 6


[Q]: Sentence: 'a couple of buses parked on the side of the street'. Find frequency of the letter 'b'
[A]: 1


[Q]: Sentence: 'a stop sign that is standing in the grass'. Find frequency of the letter 'a'
[A]:
4