Consider the problem as a variant of the Knapsack problem, where bidders (items) have multiple attributes (value, time constraints) and the goal is to maximize total value under capacity constraints.

Examine the auction's winner determination problem: prove that it reduces to the 0/1 Knapsack problem (NP-hard) by constructing a polynomial-time reduction from a known NP-hard problem.

Analyze the auction's combinatorial aspects: demonstrate that the problem is NP-hard even when restricted to a fixed number of bidders or items, by showing a reduction from the Partition problem or another strongly NP-complete problem.