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

[Q]: Sentence: 'there is a zebra that is walking enar a car'. Find frequency of the letter 'r'
[A]: 4


[Q]: Sentence: 'a close up of a train on a track in the dark'. Find frequency of the letter 'a'
[A]: 6


[Q]: Sentence: 'cat laying on the desk under laptop stand'. Find frequency of the letter 'a'
[A]:
4