TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'a small white plane sitting on top of the ocean'. Find frequency of the letter 'e'

SOLUTION: 4

PROBLEM: Sentence: 'a white police vehicle parked on a paved street'. Find frequency of the letter 'a'

SOLUTION: 4

PROBLEM: Sentence: 'customers at a large vegetable and fruit market'. Find frequency of the letter 'a'

SOLUTION:
6