TASK DEFINITION: In this task, you need to replace a letter in the sentence with another given letter.
PROBLEM: Sentence: 'a red train moves over snowy rail road tracks'. Replace the letter 'v' with 'w' in the sentence.

SOLUTION: a red train mowes ower snowy rail road tracks

PROBLEM: Sentence: 'a room with a bed, lamps, tables and pillows'. Replace the letter 's' with 'b' in the sentence.

SOLUTION: a room with a bed, lampb, tableb and pillowb

PROBLEM: Sentence: 'a boat in still water at a harbor at dusk'. Replace the letter 'r' with 'y' in the sentence.

SOLUTION:
a boat in still watey at a hayboy at dusk