Factor completely: 81x^4 – 1
a. (9x + 1)(9x – 1)
b. (9x^2 + 1)(9x^2 – 1)
c. (3x^2 + 1)^3(3x – 1)
d. (9x^2 + 1)(3x + 1)(3x – 1)

The john nash mall used 17,4000 kilowatt hours in may, with a peak load of 92 kilowatts. the demand charge is $5.95 per kilowatt, and the energy charge is $0.08 per kilowatt hour. the fuel adjustment charge is $0.017 per kilowatt hour. what is the total electricity cost for may?