TASK DEFINITION: In this task, you need to replace a letter in the sentence with another given letter.
PROBLEM: Sentence: 'a open entrance leading to a set of closed doors'. Replace the letter 'd' with 'f' in the sentence.

SOLUTION: a open entrance leafing to a set of closef foors

PROBLEM: Sentence: 'this is a seafood platter with lobster and corn on the cob'. Replace the letter 't' with 'z' in the sentence.

SOLUTION: zhis is a seafood plazzer wizh lobszer and corn on zhe cob

PROBLEM: Sentence: 'a couple of girls sitting on the curb with phones'. Replace the letter 'n' with 'i' in the sentence.

SOLUTION:
a couple of girls sittiig oi the curb with phoies