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

Example Input: Sentence: 'a woman on a cell phone on city street'. Replace the letter 'e' with 'a' in the sentence.
Example Output: a woman on a call phona on city straat

Example Input: Sentence: 'a ski slope consisting of several people wearing skis and snowboards'. Replace the letter 'e' with 's' in the sentence.
Example Output: a ski slops consisting of ssvsral psopls wsaring skis and snowboards

Example Input: Sentence: 'a man is standing at the back of a box truck'. Replace the letter 'a' with 'y' in the sentence.
Example Output:
y myn is stynding yt the byck of y box truck