Willie Stand Obtains a Patent on His New Invention, the Bipod.After

Willie Stand obtains a patent on his new invention, the bipod.After twenty years,

A) he can renew his patent
B) new entrants will begin bipod production if price exceeds average variable cost
C) new entrants will drive up the price of the bipod
D) Willie will eventually earn no more than a normal profit
E) Willie will continue to earn a positive economic profit, because entry will not affect the price of bipods