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

Example Input: Sentence: 'a person is waiting for a pizza to come out of an oven fired grill'. Replace the letter 's' with 'k' in the sentence.
Example Output: a perkon ik waiting for a pizza to come out of an oven fired grill

Example Input: Sentence: 'a group of men sitting at a desk with lap top computers'. Replace the letter 'p' with 'z' in the sentence.
Example Output: a grouz of men sitting at a desk with laz toz comzuters

Example Input: Sentence: 'a baseball themed birthday cake is on a serving tray'. Replace the letter 't' with 'b' in the sentence.
Example Output:
a baseball bhemed birbhday cake is on a serving bray