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

Sentence: 'a train on a train track going through a bunch of trees'. Find frequency of the letter 'u'
2

Sentence: 'party cakes in plastic containers, with a cake with a plastic santa claus and reindeer on top'. Find frequency of the letter 's'
6

Sentence: 'three mountain goats stand in the middle of a road'. Find frequency of the letter 'e'

4

