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

Ex Input:
Sentence: 'a man on a surfboard riding on the waters waves'. Replace the letter 's' with 'k' in the sentence.

Ex Output:
a man on a kurfboard riding on the waterk wavek

Ex Input:
Sentence: 'a bike sitting parked next to a cart in front of some boxes'. Replace the letter 't' with 'x' in the sentence.

Ex Output:
a bike sixxing parked nexx xo a carx in fronx of some boxes

Ex Input:
Sentence: 'a passenger train speeding past an empty train stop'. Replace the letter 'p' with 'l' in the sentence.

Ex Output:
a lassenger train sleeding last an emlty train stol