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

[EX Q]: Sentence: 'a group of cows that are standing in the grass'. Find frequency of the letter 'g'
[EX A]: 3

[EX Q]: Sentence: 'a yellow fire hydrant in the forefront of a roadway'. Find frequency of the letter 'r'
[EX A]: 5

[EX Q]: Sentence: 'a boy in a toy fireman's hat takes a bite out of a pastry while sitting on a counter'. Find frequency of the letter 'r'
[EX A]:
3