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

[Q]: Sentence: 'an airplane is being towed away from the jet bridge'. Find frequency of the letter 's'
[A]: 1


[Q]: Sentence: 'a white bathroom sink sitting next to a toilet'. Find frequency of the letter 'i'
[A]: 5


[Q]: Sentence: 'a woman walking with a child that is in a wheelchair'. Find frequency of the letter 'k'
[A]:
1