In this case, the base is a triangle and so its area can be found thus:
answer: c, the green line
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.
answer: what are the answer choices?