Answer:
24+24x I believe is the answer. Good luck on your test :)
Given the marginal propensity to consume (MPC), the miltiplier is given by
Multiplier = 1 / (1 - MPC)
Given that the marginal propensity to consume is 0.8, the multiplier is given by
Multiplier = 1 / (1 - 0.8) = 1 / 0.2 = 5
F(x) = x(x -1)
f(3) = 3*2 = 6
f(6) = 6*5 = 30
so f(f(3)) = 30 . . . . . selection A