TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'a close up of a train on a track in the dark'. Find frequency of the letter 'a'

SOLUTION: 6

PROBLEM: Sentence: 'a black animal in dirt area below trees and rocks'. Find frequency of the letter 'n'

SOLUTION: 3

PROBLEM: Sentence: 'a white toilet topped with vases filled with flowers'. Find frequency of the letter 'f'

SOLUTION:
2