# Given a function modeling BAC concentration after a certain time in t minutes, find how rapidly the BAC is increasing or decreasing

This question has really confused me and I hate to say that I don't even know where to start. The equation given is: C(t) = 0.0225te^(−0.0467t)

where t is measured in minutes after consumption and C is measured in mg/mL. (Round your answers to five decimal places.) (a) How rapidly was the BAC increasing after 9 minutes? (b) How rapidly was it decreasing half an hour later (t = 30)?

I tried finding the derivative, which I found to be:

.0225*e^(-.0467t)+te^(-.0467t) and then I plugged in 9 and 30 for t, but those answers were wrong. Is my derivative wrong or am I completely off on how to go about answering the question? Please help!

I can't imagine the answer would be as simple as plugging in 9 and 30 into the given equation, this is in my calculus homework that has been dealing with derivatives, particularly with the chain rule, so if that's the answer I'm going to feel pretty dumb.