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

Ex Input:
Sentence: 'busy city street with pedestrians and cars with lights all around'. Replace the letter 'r' with 'k' in the sentence.

Ex Output:
busy city stkeet with pedestkians and caks with lights all akound


Ex Input:
Sentence: 'a crowd stands under a set of lights in the ceiling and one person holds up a cell phone'. Replace the letter 'r' with 'f' in the sentence.

Ex Output:
a cfowd stands undef a set of lights in the ceiling and one pefson holds up a cell phone


Ex Input:
Sentence: 'the back end of a yellow school bus'. Replace the letter 'o' with 'd' in the sentence.

Ex Output:

the back end df a yelldw schddl bus