TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'a doorway looking into a small bathroom with white toilet'. Find frequency of the letter 'r'

SOLUTION: 2

PROBLEM: Sentence: 'a bus with two floors belonging to london country'. Find frequency of the letter 't'

SOLUTION: 4

PROBLEM: Sentence: 'a baseball player who is stepping up to home plate'. Find frequency of the letter 's'

SOLUTION:
3