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

[EX Q]: Sentence: 'a fluffy white car looking in a mirror'. Find frequency of the letter 'k'
[EX A]: 1

[EX Q]: Sentence: 'a large formal living room with yellow couches and table'. Find frequency of the letter 'v'
[EX A]: 1

[EX Q]: Sentence: 'an image of a train moving down the railroad track'. Find frequency of the letter 'a'
[EX A]:
7