TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'three young people goofing around; one of the guys has a football, the girl has a teddy bear'. Find frequency of the letter 'd'

SOLUTION: 3

PROBLEM: Sentence: 'pedestrians pass by a stop sign, some holding surfboards'. Find frequency of the letter 'n'

SOLUTION: 3

PROBLEM: Sentence: 'a young woman leaning against a wall with her hands placed on her luggage'. Find frequency of the letter 'a'

SOLUTION:
10