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

Sentence: 'man sitting on the side of a van playing the guitar'. Find frequency of the letter 'm'
1

Sentence: 'a red stop sign with street signs above it'. Find frequency of the letter 't'
5

Sentence: 'buildings surrounding two tall, skinny towers in a busy area'. Find frequency of the letter 's'

5