TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'a railroad train pulling up to the train platform'. Find frequency of the letter 'o'

SOLUTION: 3

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

SOLUTION: 3

PROBLEM: Sentence: 'a kitchen area with a refrigerator, guitar and bookshelf'. Find frequency of the letter 'a'

SOLUTION:
7