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 group of small children sitting at a table in front of a pizza'. Replace the letter 'r' with 'd' in the sentence.
Example Output: a gdoup of small childden sitting at a table in fdont of a pizza

Example Input: Sentence: 'a parking meter casts a crooked shadow upon a brick wall'. Replace the letter 'a' with 'k' in the sentence.
Example Output:
k pkrking meter cksts k crooked shkdow upon k brick wkll