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

[EX Q]: Sentence: 'a man paddle boarding by a boat dock in a city'. Find frequency of the letter 'o'
[EX A]: 3

[EX Q]: Sentence: 'a group of giraffes walk together by a hill'. Find frequency of the letter 'b'
[EX A]: 1

[EX Q]: Sentence: 'a red refrigerator freezer sitting inside of a kitchen'. Find frequency of the letter 'r'
[EX A]:
7