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: 'vintage cartoon elephant and cartoon dog paper tags'. Replace the letter 'p' with 'r' in the sentence.
Example Output: vintage cartoon elerhant and cartoon dog rarer tags

Example Input: Sentence: 'a small child brushes his teeth in the bath tub'. Replace the letter 's' with 'w' in the sentence.
Example Output:
a wmall child bruwhew hiw teeth in the bath tub