TASK DEFINITION: In this task, you need to replace a letter in the sentence with another given letter.
PROBLEM: Sentence: 'a couple walking down a sidewalk next to some graffiti'. Replace the letter 'a' with 'y' in the sentence.

SOLUTION: y couple wylking down y sidewylk next to some gryffiti

PROBLEM: Sentence: 'a living room with an orange couch and green decorations'. Replace the letter 'c' with 'm' in the sentence.

SOLUTION: a living room with an orange moumh and green demorations

PROBLEM: Sentence: 'a white car in the street it front of a cargo truck full of crates'. Replace the letter 'u' with 'e' in the sentence.

SOLUTION:
a white car in the street it front of a cargo treck fell of crates