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 guy surfs a wave with his surfboard'. Find frequency of the letter 's'
[A]: 4


[Q]: Sentence: 'a kind of messy looking bedroom in someone's house'. Find frequency of the letter 'o'
[A]:
8