TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'two bears swim in a blue pool of water'. Find frequency of the letter 'o'

SOLUTION: 4

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

SOLUTION: 4

PROBLEM: Sentence: 'a small dog is sitting in the basket of a bicycle'. Find frequency of the letter 's'

SOLUTION:
4