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

[EX Q]: Sentence: 'man in a sleeping bag on the floor using a laptop computer'. Find frequency of the letter 'i'
[EX A]: 3

[EX Q]: Sentence: 'a man in a black shirt prepares to catch a frisbee'. Find frequency of the letter 'f'
[EX A]: 1

[EX Q]: Sentence: 'subway trains are sitting idle on a railway'. Find frequency of the letter 'a'
[EX A]:
6