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 surfer is in the middle of an ocean wave'. Find frequency of the letter 'i'
[A]: 3

[Q]: Sentence: 'a canadian airplane on a run way next to a military style aircraft'. Find frequency of the letter 'r'
[A]:
5