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

Ex Input:
Sentence: 'city two way street with cars lined up on both sides'. Find frequency of the letter 'h'

Ex Output:
2

Ex Input:
Sentence: 'a large grass pasture land with sheep grazing on grass'. Find frequency of the letter 'a'

Ex Output:
7

Ex Input:
Sentence: 'an illuminated toilet with a bright light on it's lid'. Find frequency of the letter 'i'

Ex Output:
8