TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'a young boy standing in front of a counter with dougnuts'. Find frequency of the letter 'o'

SOLUTION: 6

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

SOLUTION: 2

PROBLEM: Sentence: 'three glass vases filled with bouquets of pink orchids'. Find frequency of the letter 's'

SOLUTION:
6