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

Example Input: Sentence: 'commuter trains on tracks next to paved platform'. Replace the letter 'm' with 'w' in the sentence.
Example Output: cowwuter trains on tracks next to paved platforw

Example Input: Sentence: 'this refrigerator is covered in stickers on it'. Replace the letter 't' with 'h' in the sentence.
Example Output: hhis refrigerahor is covered in shickers on ih

Example Input: Sentence: 'a small dog in the back compartment of a backpack'. Replace the letter 'c' with 'd' in the sentence.
Example Output:
a small dog in the badk dompartment of a badkpadk