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

[EX Q]: Sentence: 'a couple of people that are on a baseball field'. Find frequency of the letter 'c'
[EX A]: 1

[EX Q]: Sentence: 'a girl that has a kite in the air'. Find frequency of the letter 'r'
[EX A]: 2

[EX Q]: Sentence: 'a row of chairs sitting in front of a building'. Find frequency of the letter 'r'
[EX A]:
3