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

[Q]: Sentence: 'a white toilet sitting next to a bathroom sink'. Find frequency of the letter 'b'
[A]: 1


[Q]: Sentence: 'a man that is on his cell phone'. Find frequency of the letter 's'
[A]: 2


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