TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'a person riding a surfboard in the middle of a wave'. Find frequency of the letter 'o'

SOLUTION: 3

PROBLEM: Sentence: 'an orange cat sitting on the ground next to a  purse'. Find frequency of the letter 's'

SOLUTION: 2

PROBLEM: Sentence: 'a brown teddy bear sitting in front of an open book'. Find frequency of the letter 'y'

SOLUTION:
1