by后面加什么詞性?

　　All the statistical computations were performed by the new software system.

　　所有的統計計算均由新的軟件系統完成。

　　They won by a single goal after extra time.

　　他們在加時賽中僅踢進一球即獲勝。

　　They've increased the price by 50%.

　　他們已經把價格提高了50%。

　　Now I can walk to work instead of going by car.

　　現在我可以步行去上班，而不必開車了。

　　I'm always broke by the end of the month.

　　我總是一到月底就沒錢花了。