Gwen Taylor, apartment manager for WillowWood Apartments, wants to inform potential renters about how much electricity they can expect to use during August. She randomly selects 61 residents and discovers their average electricity usage in August to be 894 kilowatt hours (kwh). Gwen believes the variance in usage is about 131 (kwh)2 . (a) Establish an interval estimate for the average August electricity usage so Gwen can be 68.3 percent certain the true population mean lies within this interval. (b) Repeat part (a) with a 99.7 percent certainty. (c) If the price per kwh is $0.12, within what interval can Gwen be 68.3 percent certain that the average August cost for electricity will lie?