TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'a bunch of broken down trains sit in a yard'. Find frequency of the letter 'n'

SOLUTION: 5

PROBLEM: Sentence: 'a double parking meter is decorated with a picture of a girl with wings on her feet'. Find frequency of the letter 'r'

SOLUTION: 6

PROBLEM: Sentence: 'a group of people and many suitcases in a room'. Find frequency of the letter 's'

SOLUTION:
3