TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'a guy surfs a wave with his surfboard'. Find frequency of the letter 's'

SOLUTION: 4

PROBLEM: Sentence: 'the large modern train is on the train track'. Find frequency of the letter 'm'

SOLUTION: 1

PROBLEM: Sentence: 'a white bedroom with wood flooring and a large window'. Find frequency of the letter 't'

SOLUTION:
2