英语翻译我每天花半小时走路去学校（spend、take)

是不是不太清楚这些关键词怎么用?spend的主语一般都是人,和on与doing搭配.pay 的主语也是人,和for搭配.至于cost,主语就是物了,什么东西花费了某人多少钱.另外take前面一般是it,形式主语,it takes sb..(some time).. to do sth.花费某人多少时间做某事.这样解释不知清楚了没有.

答案：
Mary spent three years on wrting this book.
The book took Mary three years for finishing it.

I spent 400 yuan on the new phone.
I paid 400 yuan on the new phone.
The new phone cost me 400 yuan.

I spend half an hour on walking to school every day.
It takes me half an hour for walking to school every day.