Measures that predict how much customers and businesses will spend help forecast sales by: O a. giving a historical picture of how much those customers and businesses have spent with the company O b. forecasting how much total will be spent in different categories, so companies can calculate what percentage of that spending they can c O c.predicting whether the economy will get stronger or weaker in general d. providing points of comparison between business and retail customers that allow companies to predict sales from one based on sales fro other O e. basing predictions on figures that move as soon as market forces move