The cost of mining a ton of coal is rising faster every year.Suppose C(t)is the cost of mining a ton of coal at time t.Must C ''(t)be concave up?

Question

Quizplus · Accepted Answer

C''(t) being concave up would mean the second derivative of C(t) is positive, indicating accelerating costs. However, the statement only says costs are rising, not necessarily at an accelerating rate. C(t) could be increasing linearly or at a decreasing rate, which would not require C''(t) to be concave up.

The Cost of Mining a Ton of Coal Is Rising