Rewrite the sentence to eliminate any ambiguity.
He returned the book he borrowed last week.
He returned the book that he had borrowed from someone last week.
Complete the following task based on the instruction and optional input provided.### Instruction:
Rewrite the sentence to eliminate any ambiguity.

### Input:
He returned the book he borrowed last week.

### Output:
He returned the book that he had borrowed from someone last week.