Well depending on how you look at you could do $40 plus that extra 20% and since you said that means to add you would do the same price. as the actual price before you add that thirty 20% so you would add 40 plus 40 equals 80. If you did 25% the you would add 40 and 40 which is 80 and that's 20%out of 25% and add 5 to 80 and you get $85.
Ans: The average rate of change of function =

(in fraction)
Explanation:The average rate of change of function =

Where
b = 8 (x's upper bound)
a = 0 (x's lower bound)

Hence the average rate of change of function =

(in fraction)
Area of prism = area of base * height
= ( 312 * 5 ) * 112 = 174720 cubic inch