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

[Q]: Sentence: 'a man makes some cock tales at a desk'. Find frequency of the letter 'k'
[A]: 3


[Q]: Sentence: 'a group of tennis players on a tennis court'. Find frequency of the letter 'o'
[A]: 4


[Q]: Sentence: 'a large commercial plan flying over a city'. Find frequency of the letter 'y'
[A]:
2