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

Example Input: Sentence: 'a couple giraffes walking through a fielded area'. Replace the letter 'e' with 'c' in the sentence.
Example Output: a couplc giraffcs walking through a ficldcd arca

Example Input: Sentence: 'a baseball game is in progress at a baseball stadium'. Replace the letter 's' with 'r' in the sentence.
Example Output: a bareball game ir in progrerr at a bareball rtadium

Example Input: Sentence: 'a group of men riding on the back of motorcycles'. Replace the letter 'o' with 't' in the sentence.
Example Output:
a grtup tf men riding tn the back tf mtttrcycles