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

[EX Q]: Sentence: 'a man that is on his cell phone'. Find frequency of the letter 's'
[EX A]: 2

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

[EX Q]: Sentence: 'a white bathroom sink sitting next to a bath tub'. Find frequency of the letter 't'
[EX A]:
8