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

Example Input: Sentence: 'a police officer on a horse is riding down the street'. Replace the letter 'h' with 'a' in the sentence.
Example Output: a police officer on a aorse is riding down tae street

Example Input: Sentence: 'a fire hydrant and a rolled up fire hose'. Replace the letter 'd' with 's' in the sentence.
Example Output: a fire hysrant ans a rolles up fire hose

Example Input: Sentence: 'a guy walking down the street with sheep'. Replace the letter 'g' with 'm' in the sentence.
Example Output:
a muy walkinm down the street with sheep