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

Example Input: Sentence: 'a couple of men playing a  game of tennis'. Replace the letter 'n' with 'c' in the sentence.
Example Output: a couple of mec playicg a  game of teccis

Example Input: Sentence: 'a fire hydrant with a message painted on it'. Replace the letter 'n' with 'j' in the sentence.
Example Output: a fire hydrajt with a message paijted oj it

Example Input: Sentence: 'a railroad crossing with a stop sign and a building in the background'. Replace the letter 'g' with 'i' in the sentence.
Example Output:
a railroad crossini with a stop siin and a buildini in the backiround