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

[EX Q]: Sentence: 'a small boat and a large boat on a river near a city'. Find frequency of the letter 'a'
[EX A]: 10

[EX Q]: Sentence: 'a cat sprawls out and sleeps on its back on a lounge chair with an acorn theme'. Find frequency of the letter 'r'
[EX A]: 3

[EX Q]: Sentence: 'two woman play wii video game with wireless controllers'. Find frequency of the letter 'w'
[EX A]:
5