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

Example Input: Sentence: 'a man is standing on a snowboard, atop a mountain'. Replace the letter 'd' with 'u' in the sentence.
Example Output: a man is stanuing on a snowboaru, atop a mountain

Example Input: Sentence: 'a clock mounted above a door entrance with windows'. Replace the letter 's' with 'l' in the sentence.
Example Output: a clock mounted above a door entrance with windowl

Example Input: Sentence: 'a street sign next to a miles per hour sign'. Replace the letter 'e' with 'g' in the sentence.
Example Output:
a strggt sign ngxt to a milgs pgr hour sign