Saving for Retirement
Borrowing to Go to School
Although the income effect can reverse the substitution effect, we think it generally does not because most people have income in both periods. If the consumption point is near the pivot point, the slope changes, causing a substitution effect, but the movement in or out is minimal.
The answer is most often a diagram in economics. Words is seldom the best strategy if you are clueless.
Avoid the postage stamp diagram, and do not make a mess. Label all axes and curves, and indicate which way things shift.
One important exam strategy is "Do not miss the easy ones."
This mortgage refinancing question (8% to 6%) is an easy one.