you're given the voltage and the current as functions of time, the product of these two gives an expression for the power.
P = I V
Now take the derivative with respect to time, and solve for time, remember from calc, that the critical points are those for which the slope of the tangent line is zero. Once you found a time, remember that for t<0, there's no current -> no power. So this time will answer (a), now take your result for (a) and substitute it into your equation for P, to get the maximum power. For (c) then how do you find the total power delivered to any circuit element. Hint: you have enough information to find this one too. hope this helps, sincerely, x