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

[Q]: Sentence: 'two people are riding on canoes down a river'. Find frequency of the letter 'e'
[A]: 5


[Q]: Sentence: 'an image of a street sign with a corner restaurant'. Find frequency of the letter 'u'
[A]: 1


[Q]: Sentence: 'a pile of celery sitting next to piles of other vegetables'. Find frequency of the letter 'e'
[A]:
9