Coal Mine Rescue Field Test 5 Taken from the 2018 Kentucky River Mine Rescue Contest held in Hazard, Kentucky Progress Indicator: Question 5 of 10 5.  An AC circuit has 40-ohm R, 90-ohm XL, and 60-ohm XC, all in series.  The impedance equals: Choices: 50 ohms 70.7 ohms 110 ohms 190 ohms