TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'a group of people standing on grass with a train in the background'. Find frequency of the letter 'n'

SOLUTION: 6

PROBLEM: Sentence: 'a airplane view of a big factory some people and cars'. Find frequency of the letter 'f'

SOLUTION: 2

PROBLEM: Sentence: 'a plate of bananas and a spoon of peanut butter on a table'. Find frequency of the letter 'a'

SOLUTION:
10