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

Ex Input:
Sentence: 'a baby calf has a tag on its right ear'. Find frequency of the letter 'n'

Ex Output:
1

Ex Input:
Sentence: 'a woman walking with a child that is in a wheelchair'. Find frequency of the letter 'k'

Ex Output:
1

Ex Input:
Sentence: 'a living room with white walls and wood flooring'. Find frequency of the letter 'i'

Ex Output:
5