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

Example Input: Sentence: 'a couple of kids with rackets on a court'. Replace the letter 'u' with 'd' in the sentence.
Example Output: a codple of kids with rackets on a codrt

Example Input: Sentence: 'a rose that is sitting in a vase'. Replace the letter 'r' with 'j' in the sentence.
Example Output: a jose that is sitting in a vase

Example Input: Sentence: 'a couple of vases that have some flowers in it'. Replace the letter 'f' with 'x' in the sentence.
Example Output:
a couple ox vases that have some xlowers in it