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: 'small kit bathroom sink with purple walls and lights on it'. Replace the letter 'o' with 'r' in the sentence.

SOLUTION: small kit bathrrrm sink with purple walls and lights rn it

PROBLEM: Sentence: 'a brown and white cat on carpet with wall in background'. Replace the letter 'b' with 's' in the sentence.

SOLUTION:
a srown and white cat on carpet with wall in sackground