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

Example Input: Sentence: 'a building has a clock on the top of it'. Replace the letter 'l' with 'x' in the sentence.
Example Output: a buixding has a cxock on the top of it

Example Input: Sentence: 'a couple of kids with rackets on a court'. Replace the letter 'u' with 'd' in the sentence.
Example Output: a codple of kids with rackets on a codrt

Example Input: Sentence: 'a man on the beach kicking the sand'. Replace the letter 'n' with 'y' in the sentence.
Example Output:
a may oy the beach kickiyg the sayd