TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'a passenger bus that is driving down the street'. Find frequency of the letter 'r'

SOLUTION: 3

PROBLEM: Sentence: 'a girl sits on a surfboard and smiles'. Find frequency of the letter 'i'

SOLUTION: 3

PROBLEM: Sentence: 'a man on a surfboard in the midst of an ocean wave'. Find frequency of the letter 'n'

SOLUTION:
5