1. The problem statement, all variables and given/known data Help with this question would be greatly appreciated as I have attempted it many times without success and I don't know where I'm going wrong. The quantity of charge q (in coulombs) that has passed through a surface of area 1.90 cm2 varies with time according to the equation q = 8t^3 + 7t + 6, where t is in seconds. What is the instantaneous current through the surface at t = 0.900 s? 2. Relevant equations I = Q/t dQ/dt 3. The attempt at a solution I would think that you find dQ/dt which would give 24t^2 + 7, substitute 0.9 into t which equals the charge and then divide that by the time to find instantaneous current. Current was = 20.15A, which was incorrect I also tried substituting 0.9 into 8t^3 + 7t + 6 and then dividing by time. Here the current was = 29.37A. Incorrect as well.