In this task, you need to replace a letter in the sentence with another given letter.

Sentence: 'a couple walking down a sidewalk next to some graffiti'. Replace the letter 'a' with 'y' in the sentence.
y couple wylking down y sidewylk next to some gryffiti

Sentence: 'a couple of giraffes eat some food out of a trey'. Replace the letter 'f' with 'e' in the sentence.
a couple oe giraeees eat some eood out oe a trey

Sentence: 'three way stop sign on a tree lined street'. Replace the letter 'r' with 'm' in the sentence.

thmee way stop sign on a tmee lined stmeet