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

Example Input: Sentence: 'a couple of giraffes eat some food out of a trey'. Replace the letter 'f' with 'e' in the sentence.
Example Output: a couple oe giraeees eat some eood out oe a trey

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 young boy riding skis across a snow covered slope'. Replace the letter 'y' with 'u' in the sentence.
Example Output:
a uoung bou riding skis across a snow covered slope