An electric utility company determines the monthly bill by charging 76.7 cents per kilowatt‐hour (KWh) used plus a base charge of $16.37 per month. Thus the monthly charge is given by the function f (W )  0.767W  16.37 dollars where W is the number of kilowatt‐hours. a. Find f (1000) and explain what it means. To find f (1000) , we need to substitute W  1000 into the formula. f (1000)  0.767 1000   16.37 dollars
 783.37 dollars
This tells us that an input of 1000 kilowatt‐hours yields a monthly charge of $783.37. So if you used 1000 kilowatt‐hours, the utility would charge you $783.37. b. What is the monthly charge if 1500 KWh are used? The question specifies W  1500 . To find the monthly charge, find f (1500)  0.767 1500   16.37 dollars
 1166.80 dollars