Central States Electric Company estimates its demand trend line (in millions of kilowatt hours) to be: D = 77 +0.430 where refers to the sequential quarter number and Q=1 for winter 1986. In addition, the multiplicative seasonal factors are as follows: Quarter Factor (Index) Winter .8 Spring 1.1 Summer 1.4 Fall .7 Forecast energy use for the four quarters of 2011, beginning with winter.