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

[EX Q]: Sentence: 'a red and white train passing a train station'. Find frequency of the letter 'a'
[EX A]: 7

[EX Q]: Sentence: 'a tall building with antenna stands before a jet flying in the background'. Find frequency of the letter 't'
[EX A]: 6

[EX Q]: Sentence: 'a dog as seen in a rear view mirror of a vehicle'. Find frequency of the letter 's'
[EX A]:
2