If the market is fully efficient, then an announcement by a firm of a new product with a high net present value will cause the market price of that firm's stock to:

a.immediately decline to a new level equivalent to the decreased value of the firm.

b.rise gradually over the next few days.

c.decline gradually over the next few days.

d.remain constant.

e.immediately increase to a new level equivalent to the increased value of the firm.