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

Input: Consider Input: Sentence: 'a guy looking at a tennis ball with a goofy look'. Replace the letter 'a' with 'x' in the sentence.

Output: x guy looking xt x tennis bxll with x goofy look

Input: Consider Input: Sentence: 'a couple of men playing a game of tennis'. Replace the letter 'n' with 'c' in the sentence.

Output: a couple of mec playicg a game of teccis

Input: Consider Input: Sentence: 'a couple of bags that are against the wall'. Replace the letter 'u' with 'c' in the sentence.
Output: a cocple of bags that are against the wall