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

[Q]: Sentence: 'a man and several white red and blue airplanes'. Find frequency of the letter 'u'
[A]: 1


[Q]: Sentence: 'a group of men standing around a table cutting a cake'. Find frequency of the letter 'g'
[A]: 3


[Q]: Sentence: 'a man on a skateboard doing tricks, watched by an audience'. Find frequency of the letter 'e'
[A]:
4