TASK DEFINITION: In this task, you need to count the number of times the given letter appears in the given sentence.
PROBLEM: Sentence: 'a construction sign is displayed on a street'. Find frequency of the letter 'i'

SOLUTION: 4

PROBLEM: Sentence: 'a man using a video game controller in a room'. Find frequency of the letter 'n'

SOLUTION: 4

PROBLEM: Sentence: 'a large grey plane sitting on a runway in fog'. Find frequency of the letter 'y'

SOLUTION:
2