instruction:
In this task, you need to count the number of times the given letter appears in the given sentence.
question:
Sentence: 'three men in military suits are sitting on a bench,'. Find frequency of the letter 'a'
answer:
3


question:
Sentence: 'a man skating down a stair rail in front of a bunch of people'. Find frequency of the letter 'o'
answer:
5


question:
Sentence: 'two commuter trains passing each other on the tracks'. Find frequency of the letter 'a'
answer:

4