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

Example Input: Sentence: 'three laptops are turned on lined up on a table'. Replace the letter 't' with 'g' in the sentence.
Example Output: ghree lapgops are gurned on lined up on a gable

Example Input: Sentence: 'an old rusty car sits outside of an old building'. Replace the letter 'o' with 'r' in the sentence.
Example Output: an rld rusty car sits rutside rf an rld building

Example Input: Sentence: 'a group of zebras standing in front of some trees'. Replace the letter 'r' with 'a' in the sentence.
Example Output:
a gaoup of zebaas standing in faont of some taees