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

[EX Q]: Sentence: 'a close up of a train on a track in the dark'. Find frequency of the letter 'a'
[EX A]: 6

[EX Q]: Sentence: 'a row of vintage cars in a grassy field'. Find frequency of the letter 'v'
[EX A]: 1

[EX Q]: Sentence: 'two pizzas sitting on top of a bbq grill'. Find frequency of the letter 's'
[EX A]:
2