根据要求改写句子。

1.He spent 10 yuan buying the pen . (改为同义句)

   He         ___10 yuan  __           the pen.

2.Finishing the work is hard . (改为同义句)

                 _hard             _ the work.

3.Why not go shopping ?(改为同义句)  

                 _                    shopping ?

4.If you aren't quick , you'll miss the bus . (改为同义句) 

                 _, __            you'll miss the bus .