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

Example Input: Sentence: 'a person under an open umbrella in the sand'. Replace the letter 'd' with 'h' in the sentence.
Example Output: a person unher an open umbrella in the sanh

Example Input: Sentence: 'a red stop sign sitting on the side of a road'. Replace the letter 'r' with 'o' in the sentence.
Example Output: a oed stop sign sitting on the side of a ooad

Example Input: Sentence: 'a man looks upward while a large teddy bear sits in his lap'. Replace the letter 'i' with 'd' in the sentence.
Example Output:
a man looks upward whdle a large teddy bear sdts dn hds lap