TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'a green bus driving in a street filled with heavy traffic'. Find frequency of the letter 'v'

SOLUTION: 2

PROBLEM: Sentence: 'a woman walking with a child that is in a wheelchair'. Find frequency of the letter 'k'

SOLUTION: 1

PROBLEM: Sentence: 'two road workers are standing by a red light with a sign'. Find frequency of the letter 's'

SOLUTION:
3