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

Example Input: Sentence: 'a man is standing with this luggage next to a railroad track'. Replace the letter 'g' with 'l' in the sentence.
Example Output: a man is standinl with this lullale next to a railroad track

Example Input: Sentence: 'a couple of giraffe standing next to each other in a forest'. Replace the letter 'a' with 'w' in the sentence.
Example Output: w couple of girwffe stwnding next to ewch other in w forest

Example Input: Sentence: 'three young men stand together with an umbrella'. Replace the letter 's' with 'w' in the sentence.
Example Output:
three young men wtand together with an umbrella