Answer:
d. increase by 40 units
Explanation:
We post the increments in the formula and check;
Qd`` = 60 - 60(p + 2) + 2(Y + 80)
Qd`` = 60 - 120 - 60p + 160 + 2Y
Qd`` = 100 - 60p + 2Y
Qd = 60 - 60p + 2Y
we subtract one from another and the difference is the incremental oor decremental that arise as a result of the changes:
100 - 60 - 60p - (-60p) + 2y - 2y = 40