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

Example Input: Sentence: 'a dog wearing a hat on top of it's head'. Replace the letter 'g' with 'o' in the sentence.
Example Output: a doo wearino a hat on top of it's head

Example Input: Sentence: 'a row of lawn chairs with umbrellas over them'. Replace the letter 'e' with 'x' in the sentence.
Example Output: a row of lawn chairs with umbrxllas ovxr thxm

Example Input: Sentence: 'a black luggage case sitting in the middle of a room'. Replace the letter 'b' with 's' in the sentence.
Example Output:
a slack luggage case sitting in the middle of a room