The voltage V in a circuit that satisfies the law V = IR is slowly dropping as the battery wears out. At the same time, the resistance R is increasing as the resistor heats up. Use the equation dV dt = ∂V ∂I dI dt + ∂V ∂R dR dt to find how the current I is changing at the instant when R = 600 ohms, I = 0.04 amps, dR/dt = 0.5 ohms/sec, and dV /dt = −0.01 volts/sec. Hint: We need to find the rate of change of I, with respect to time. Find the partial derivatives of V with respect to I and R, then substitute into the equation for dV /dt.