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

[Q]: Sentence: 'a man flying through the air on a bicycle'. Find frequency of the letter 'u'
[A]: 1


[Q]: Sentence: 'the small black and white dog holds onto a frisbee'. Find frequency of the letter 'h'
[A]: 3


[Q]: Sentence: 'a half eaten banana, a cup, mints and keyboard on a desk'. Find frequency of the letter 'd'
[A]:
3