TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'a man holding a baseball bat an playing baseball'. Find frequency of the letter 'l'

SOLUTION: 6

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: 'a blue commuter train traveling through a rural countryside'. Find frequency of the letter 'u'

SOLUTION:
5