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 sitting inside a green military truck talking to someone'. Find frequency of the letter 'i'

SOLUTION: 7

PROBLEM: Sentence: 'an old man in a funny hat eating'. Find frequency of the letter 't'

SOLUTION:
2