TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'a big bear walks through some grass'. Find frequency of the letter 'a'

SOLUTION: 4

PROBLEM: Sentence: 'a man pushing a cart full of bananas'. Find frequency of the letter 'u'

SOLUTION: 2

PROBLEM: Sentence: 'a man sits on a couch while a dog lies on the floor'. Find frequency of the letter 'e'

SOLUTION:
3