Answer:
B. shifts rightward, and the point at which the PPF touches the good-X axis has to be something more than 40 units of good X and the point at which the PPF touches the good-Y axis has to be something more than 60 units
Explanation:
PPF is the graphical representation of two goods combinations which an economy can produce given resources & technology.
It is downward sloping because of two goods inverse relation given same resources & technology.
The points at which PPF touches both axis represents maximum amount of that axis good which can be produced by given resources & technology , Points on PPF reflect full efficient utilisation of resources. Points inside PPF reflect underutilisation of resources. Points outside PPF reflect unattainable combinations outside economy's productive capacity, given resources & technology unless either of them grow.
Resource increase usable for production of both goods: shifts the PPF outwards/ rightwards & the maximum potential production of both goods increases. PPF touching axis points increases from pervious at each axis - more than 40 at good X axis, more than 60 at Y axis.