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

[EX Q]: Sentence: 'large grassy pasture filled with trees and a single horse'. Find frequency of the letter 'l'
[EX A]: 4

[EX Q]: Sentence: 'a double-decker bus covered in children's illustrations driving next to a van'. Find frequency of the letter 'a'
[EX A]: 4

[EX Q]: Sentence: 'a photo of three giraffes walking on the plains'. Find frequency of the letter 'r'
[EX A]:
2