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

[Q]: Sentence: 'a bed with a mattress that has nothing on it'. Find frequency of the letter 'a'
[A]: 5


[Q]: Sentence: 'a man in a black wet suit rides an orange surfboard on the water'. Find frequency of the letter 'o'
[A]: 3


[Q]: Sentence: 'a giraffe is standing near some green, leafy trees'. Find frequency of the letter 'a'
[A]:
5