$22.$evpi

The firm could build a medium$-$size facility as a hedge: if demand turns out to be low, its net present value is estimated at $$22$ million; if demand turns out to be high, the firm could do nothing and realize a net present value of $$46$ million, or it could expand and realize a net present value of $$50$ million.

If the firm builds a large facility and demand is low, the net present value will be $-$$$20$ million, whereas high demand will result in a net present value of $$72$ million.