TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'a girl playing with a frisbee while people watch'. Find frequency of the letter 'e'

SOLUTION: 5

PROBLEM: Sentence: 'pedestrian in stripe clothing standing on street corner'. Find frequency of the letter 's'

SOLUTION: 4

PROBLEM: Sentence: 'people trek up the snowy mountain side with skis'. Find frequency of the letter 's'

SOLUTION:
4