[-71 Points] DETAIL Cell Phone Ad Spending A certain industry's ad spending between 2005 (t = 1) and 2011 (t = 7) is projected to be S(t) = 0.860.91 (1 sts 7) where S(t) is measured in billions of dollars and t is measured in years. What is the projected average spending per year on these ads between 2005 and 2011? (Round your answer to two decima places.) $ billion/yr Need Help? Read It