TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'a piece of film shows two street signs crossing each other'. Find frequency of the letter 'f'

SOLUTION: 2

PROBLEM: Sentence: 'a yellow and green train on a train track in a wooded area'. Find frequency of the letter 'o'

SOLUTION: 4

PROBLEM: Sentence: 'a brown horse is standing in its pen with a cover on'. Find frequency of the letter 'o'

SOLUTION:
4