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

[Q]: Sentence: 'some people sitting on surfboards in the water'. Find frequency of the letter 't'
[A]: 4


[Q]: Sentence: 'two young ladies that are dancing in the room together'. Find frequency of the letter 'a'
[A]: 4


[Q]: Sentence: 'the man is waiting for the train to arrive'. Find frequency of the letter 'i'
[A]:
5