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 man with headphones on is hunched over a sink while being recorded'. Find frequency of the letter 'd'
[A]: 4

[Q]: Sentence: 'dull red train, 54, between grass and trees'. Find frequency of the letter 'r'
[A]:
4