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

Example Input: Sentence: 'two kids sitting on a child's bed and smiling'. Replace the letter 't' with 's' in the sentence.
Example Output: swo kids sissing on a child's bed and smiling

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: 'two men are riding in a carriage pulled by horses'. Replace the letter 'e' with 'n' in the sentence.
Example Output:
two mnn arn riding in a carriagn pullnd by horsns