Answer:
Carol's total consumption will increase by $300
Carol's marginal propensity to save (MPS) = ($100 + $100) / ($1,700 - $1,200) = $200 / $500 = 0.4 or 40%
So her marginal propensity to consume (MPC) = 1 - 0.4 = 0.6 or 60%
If Carol's disposable income increases by $500, then her consumption will increase by $300 (= 60% x $500).
The marginal propensity to consume (MPC) is the proportion of a change in income that is spent.