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

Example Input: Sentence: 'a few zebras that are next to each other'. Replace the letter 'o' with 'u' in the sentence.
Example Output: a few zebras that are next tu each uther

Example Input: Sentence: 'a couple of people that are petting a horse'. Replace the letter 'e' with 'p' in the sentence.
Example Output: a couplp of ppoplp that arp pptting a horsp

Example Input: Sentence: 'a couple of ducks standing on the side of a road'. Replace the letter 'd' with 'l' in the sentence.
Example Output:
a couple of lucks stanling on the sile of a roal