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

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: 'nine geese flying south for the winter months'. Replace the letter 't' with 'f' in the sentence.
Example Output: nine geese flying soufh for fhe winfer monfhs

Example Input: Sentence: 'a man standing on to of a snow covered ski slope'. Replace the letter 'n' with 'r' in the sentence.
Example Output:
a mar stardirg or to of a srow covered ski slope