Christopher is going to install wallpaper on the four walls of his room. two of the walls are 14 feet long by 9 feet high. the other two walls are 20 feet long by 9 feet high. his options at the wallpaper store are below. one single roll of wallpaper costs $20 and covers 18 square feet of area. one double roll of wallpaper costs $40 and covers 54 square feet of area. what is the minimum cost of installing the wallpaper on the four walls of christopher's room?

4444444444444 i think

answer: c, the green line

step-by-step explanation:

there is no black line, eliminate b.

simple interest implies periodic payments, but the red line shows no payments, eliminate d.

simple interest has equal payments. if paid say every day, the graph is about a straight line (actually a stairstep).

the yellow line is not straight, eliminate a.

check: the green line is straight, answer is c.

simple interest with positive interest rate gives a straight line sloping up to the right. green line:

g(t) = $100 + ($200-$100) ÷ (20 years) × (t years)

= $100 + (4%/year) × ($100)(t years)

incidentally, the yellow line curving upward represents continuously compounded interest

y = $100 × 2^(t years / (14 assuming the yellow line hits $200 at 14 years. 2^0 is 1, so y(0) = $100; 2^(14/14) is 2, so y(14) = $200.