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

[Q]: Sentence: 'a ready to eat pizza on a rack'. Find frequency of the letter 'r'
[A]: 2


[Q]: Sentence: 'a person riding a surfboard in the middle of a wave'. Find frequency of the letter 'o'
[A]: 3


[Q]: Sentence: 'a small child in a red shirt is holding a blue frisbee'. Find frequency of the letter 's'
[A]:
4