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

Sentence: 'a microwave oven with a yellow note on the door'. Find frequency of the letter 'w'
3

Sentence: 'a cat that is standing next to an open suitcase'. Find frequency of the letter 'e'
3

Sentence: 'a train car sitting in front of a large building and being loaded with items'. Find frequency of the letter 'e'

4