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

Example Input: Sentence: 'a group of three giraffes standing around a fence'. Replace the letter 't' with 'a' in the sentence.
Example Output: a group of ahree giraffes saanding around a fence

Example Input: Sentence: 'sliced pizza served on plate next to beverage at table'. Replace the letter 'n' with 'y' in the sentence.
Example Output: sliced pizza served oy plate yext to beverage at table

Example Input: Sentence: 'a couple of broke down trucks sit in a back yard'. Replace the letter 'e' with 'z' in the sentence.
Example Output:
a couplz of brokz down trucks sit in a back yard