You can decrease the width of a confidence interval (make the confidence
interval smaller) by

F(x) =2.96.(1.04)ˣ, where x is the number of monthsprice at the origin, when x = 0→ f(x) = 2.96(1.04)⁰  →f(x) = 2.96(remember any number with exponent 0 gives 1).price after 1 month (x=1)  → f(x) =2.96.(1.04)¹ = 3.0784increase of cost = (3.0784-.96)/2.96 = 0.04 or 4% increase.however you could have noticed it from the formula: f(x) =2.96.(1.04)ˣ = 2.96(1+0.04)ˣ (and the 0.04 or 4% is the increase over 1.sorry for the 2nd part, i am confused with your "table" . i have to see a proper table in order to you