An engineer is the lead designer for a new pedestrian bridge.
The project manager, under pressure to meet a tight deadline, instructs the engineer to approve a design that uses a lower grade of steel than specified in the original, approved plans.
The engineer's analysis shows the lower-grade steel meets the minimum safety requirements by a very small margin but significantly reduces the bridge's expected lifespan and durability.
Which of the following is the engineer's most ethical course of action?