How Do You Calculate the Instantaneous Power of a Car Engine?

[404]

Car with mass of 1500kg, accelerates from 0 to 18 uniformly in 12 sec. Air drag is 400 N. Find the inst. Power output of engine at t = 12s. just before car stops accelerating...

Well I found the average power to be 23850 w, but how would you get the instantaneous?

 

[courtrigrad]

$$P = \lim_{\Delta T\rightarrow 0} \frac{\Delta W}{\Delta t} = \frac{dW}{dt}$$

I think $$P = F\bullet v$$ for instantaneous power.