the profit maximizing output of Firm 2 taking Q1 as given.

是已知Q1时能最大化厂家2利益的产量
All right, so we've done the second step for this already,

好的现在我们也完成了对这个问题的第二个准备
we already know what Firm 2's going to do.

我们知道了厂家2应该怎么做
Of course, the additional step here now is that

然而牵扯出来的问题是
Firm 1 knows that Firms 2's going to do it.

这样一来厂家1也就知道厂家2会怎么做
Firm 1's going to move first and Firm 1 knows

厂家1会先采取行动因为他知道
that after she sets her quantity Q1,

一旦他设定了产量Q1
Firm 2 will respond by choosing her corresponding quantity,

厂家2就会回应一个相对合作的产量
which is the best response to it.

即针对它的最佳对策
So if Firm 1 knows that if Firm 1 were to choose this quantity,

所以如果厂家1选择了他的这个产量
then Firm 2 will respond by choosing this quantity,

厂家2就会选择这个产量
and Firm 1 knows that if she chose this smaller quantity,

如果厂家1选择稍少的产量