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 grey hummingbird by fence and tree branches'. Find frequency of the letter 'y'

SOLUTION: 2

PROBLEM: Sentence: 'an empty bench next to a snowy lake'. Find frequency of the letter 'm'

SOLUTION:
1