TASK DEFINITION: In this task, you need to replace a letter in the sentence with another given letter.
PROBLEM: Sentence: 'a couple of horses with carriages at a building'. Replace the letter 'u' with 'm' in the sentence.

SOLUTION: a comple of horses with carriages at a bmilding

PROBLEM: Sentence: 'a person flying a kite on the beach  between some trees'. Replace the letter 's' with 'k' in the sentence.

SOLUTION: a perkon flying a kite on the beach  between kome treek

PROBLEM: Sentence: 'a man sis with his head in his hands with a cell phone to his ear'. Replace the letter 'a' with 'r' in the sentence.

SOLUTION:
r mrn sis with his herd in his hrnds with r cell phone to his err