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

Input: Consider Input: Sentence: 'a small bird perched on some thin branches'. Replace the letter 'a' with 'f' in the sentence.

Output: f smfll bird perched on some thin brfnches

Input: Consider Input: Sentence: 'a plate topped with a bacon and broccoli salad'. Replace the letter 'o' with 't' in the sentence.

Output: a plate ttpped with a bactn and brtcctli salad

Input: Consider Input: Sentence: 'the double decker bus is not in service'. Replace the letter 'b' with 'n' in the sentence.
Output: the dounle decker nus is not in service