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

Example Input: Sentence: 'a crooked street sign on a damaged sidewalk'. Replace the letter 'm' with 'u' in the sentence.
Example Output: a crooked street sign on a dauaged sidewalk

Example Input: Sentence: 'a couch, footrest, tv and other furniture are arranged in a living room'. Replace the letter 'o' with 'g' in the sentence.
Example Output: a cguch, fggtrest, tv and gther furniture are arranged in a living rggm

Example Input: Sentence: 'a cat is playing with a backpack strap'. Replace the letter 'k' with 'b' in the sentence.
Example Output:
a cat is playing with a bacbpacb strap