Task: Reasoning / Round Up Error
User instruction:
They want to empty 42 bookcases each with 38 shelves from the library. Each shelf holds 25 books, and each book weighs an average of 0.8 kg. If a book cart can carry up to 120 kg, what is the minimum number of carts needed? (Round up if necessary.)

Evaluation criteria:
The correct answer is 266.
If intermediate steps are provided, they must yield the same intermediate results as below and be logically consistent with the final answer (266).

- The total number of books is about 39,900.
- The total weight is 31,920 kg.
- The remainder must be 0.