Part of a circuit has two resistors connected in parallel as shown in the figure. R1 is a constant resistor of 10 ohm, while R2 is a variable resistor with resistance that varies at a rate of 2 ohms per minute. The total, or effective, resistance, R, provided by this circuit is given by:
1/R= 1/R1+1/R2

At what rate does the effective resistance change when R2 is 100 ohms? Round off your answer to four decimal places.