Chapter 13.5, Problem 36ES

The voltage, V (in volts), across a circuit is given by Ohm's law: $V=IR,$ where I is the current (in amperes) flowing through the circuit and R is the resistance (in ohms). If two circuits with resistances $R_1\text{and}{R}_2$ are connected in parallel, then their combined resistance, R, is given by $\frac{1}{R}=\frac{1}{R_1}+\frac{1}{R_2}$ Suppose that the current is 3 amperes and is increasing at ${10}^{-2}$ ampere/s, $R_1$ is 2 ohms and is increasing at 0.4 ohm/s, and $R_2$ is 5 ohms and is decreasing at 0.7 ohm/s. Estimate the rate at which the voltage is changing.