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

[EX Q]: Sentence: 'man in red shirt with black suitcase standing outside of building'. Find frequency of the letter 'i'
[EX A]: 8

[EX Q]: Sentence: 'an area that has surrounded by a metal fence'. Find frequency of the letter 'o'
[EX A]: 1

[EX Q]: Sentence: 'a person wearing a helmet and goggles snowboarding'. Find frequency of the letter 'e'
[EX A]:
5