某房地产26000m²，拥有两部电梯，售价6000元/m²，若增加安装第三部电梯，安装费用300万元，价格可以达到6300元/m²，则第三部电梯的投资价值为( )元。

A．3000000

B．4800000

C．15600000

D．163800000

With all its advantages, the computer is by no means without its ______.

A. boundaries
B. restraints
C. confinements
D. limitations