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 on a skateboard going down a ramp'. Find frequency of the letter 'n'
[A]: 4


[Q]: Sentence: 'a microwave with a radioactive warning sticker on the front'. Find frequency of the letter 'r'
[A]:
5