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

[EX Q]: Sentence: 'a young girl is brushing her teeth in this dated photo'. Find frequency of the letter 't'
[EX A]: 5

[EX Q]: Sentence: 'this yellow fire hydrant sits in a grass field'. Find frequency of the letter 'i'
[EX A]: 5

[EX Q]: Sentence: 'rows of gray and black keyboards make up several different pictures'. Find frequency of the letter 'r'
[EX A]:
6