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 boat and a large boat on a river near a city'. Find frequency of the letter 'a'

SOLUTION: 10

PROBLEM: Sentence: 'a stop sign next to houses with christmas lights'. Find frequency of the letter 's'

SOLUTION: 7

PROBLEM: Sentence: 'a large gathering of people at an indoor event'. Find frequency of the letter 'e'

SOLUTION:
6