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

Sentence: 'a couple of buildings that has a bus out front'. Find frequency of the letter 'a'
4

Sentence: 'there is a stop sign that has a reflection in a puddle'. Find frequency of the letter 'e'
5

Sentence: 'a yellow fire hydrant in the forefront of a roadway'. Find frequency of the letter 'r'

5