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

Ex Input:
Sentence: 'a close shot of a stop sign near a building'. Replace the letter 'b' with 'u' in the sentence.

Ex Output:
a close shot of a stop sign near a uuilding

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: 'toy bear on a toy motorcycle on a table with a tv and room in background'. Replace the letter 'b' with 'v' in the sentence.

Ex Output:
toy vear on a toy motorcycle on a tavle with a tv and room in vackground