TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'a green bus driving in a street filled with heavy traffic'. Find frequency of the letter 'v'

SOLUTION: 2

PROBLEM: Sentence: 'two zebras standing around while a third zebra drinks from a pond'. Find frequency of the letter 's'

SOLUTION: 3

PROBLEM: Sentence: 'a woman and a child walking down a street with a kite'. Find frequency of the letter 'n'

SOLUTION:
4