Last week a production worker had gross earnings of $390. if she worked more than 40hours last week and was paid 1.5times her egular hourly rate for each hour worked in excess of 40 hours,how many hours did she work last week?

请问大家，怎么才能判断出，这里是说明她已经干了40小时以上。而不是我理解的 可能干了40小时以上那？

如果是我说得情况，文章怎么改写那？？？

现在弄得草木皆兵 唉～～～

并不是说她已经干了40个小时以上，而是一个条件句。

表达成数学含义就是：当工作时间t<=40，egular hourly rate=r，gross earnings=t*r;当t>50, egular hourly rate=40r+(t-40)*1.5r