A thermistor is connected in series with a variable resistance Rs such that the current through the thermistor is limited to 1 mA when the battery voltage is 9 V and the thermistor is at room...

A thermistor is connected in series with a variable resistance Rs such that the current through the thermistor is limited to 1 mA when the battery voltage is 9 V and the thermistor is at room temperature of 20◦ C (see Figure II.2). The thermistor is characterized by a resistance of 2 kΩ at 20◦ C and a β value of 3000 K. Determine the value of the series resistance when the thermistor is at 20◦ C. The thermistor is exposed to an environment at 40◦ C. The variable resistance is to be adjusted such that the current is again 1 mA. What is the series resistance?