TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'a stop sign next to houses with christmas lights'. Find frequency of the letter 's'

SOLUTION: 7

PROBLEM: Sentence: 'a street at night with trees and streetlights on'. Find frequency of the letter 't'

SOLUTION: 9

PROBLEM: Sentence: 'old photograph of baseball team posed on a set of steps'. Find frequency of the letter 'o'

SOLUTION:
7