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

Example Input: Sentence: 'a kid is sitting on a skateboard outside'. Replace the letter 'd' with 'a' in the sentence.
Example Output: a kia is sitting on a skateboara outsiae

Example Input: Sentence: 'people are standing outside in the parking lot'. Replace the letter 'i' with 'z' in the sentence.
Example Output: people are standzng outszde zn the parkzng lot

Example Input: Sentence: 'a train traveling on a train track near a field with cows in it'. Replace the letter 'n' with 'y' in the sentence.
Example Output:
a traiy traveliyg oy a traiy track year a field with cows iy it