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

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

[EX Q]: Sentence: 'a stop sign next to houses with christmas lights'. Find frequency of the letter 's'
[EX A]: 7

[EX Q]: Sentence: 'a little boy playing in his yard with a baseball bat'. Find frequency of the letter 'i'
[EX A]:
5