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

[Q]: Sentence: 'a little boy that has a toothbrush in his mouth'. Find frequency of the letter 'r'
[A]: 1

[Q]: Sentence: 'the small black and white dog holds onto a frisbee'. Find frequency of the letter 'h'
[A]: 3

[Q]: Sentence: 'a couple of women standing next to a couple of soldiers'. Find frequency of the letter 'i'
[A]:
2