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

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


[Q]: Sentence: 'some people sitting on surfboards in the water'. Find frequency of the letter 't'
[A]: 4


[Q]: Sentence: 'halved sandwiches sit next to a pile of chips and a drink'. Find frequency of the letter 'n'
[A]:
4