TASK DEFINITION: In this task, you need to replace a letter in the sentence with another given letter.
PROBLEM: Sentence: 'a couple of white street signs sitting on top of a pole'. Replace the letter 'n' with 't' in the sentence.

SOLUTION: a couple of white street sigts sittitg ot top of a pole

PROBLEM: Sentence: 'a row of lawn chairs with umbrellas over them'. Replace the letter 'e' with 'x' in the sentence.

SOLUTION: a row of lawn chairs with umbrxllas ovxr thxm

PROBLEM: Sentence: 'a man and a woman ride a motorcycle down a street'. Replace the letter 'a' with 'u' in the sentence.

SOLUTION:
u mun und u womun ride u motorcycle down u street