<P>John Henry, an avid gardener, has found that the number of happy plants, <I >h</I>, depends on the amount of light, <I >l,</I> and water, <I >w</I>. The production function is as follows: <I >h</I> = min {<I >l</I>, 2<I >w</I>}.</P>
<P>If each unit of light costs <I >w</I><SUB>1</SUB>, and each unit of water costs <I >w</I><SUB> 2</SUB>, derive John’s cost function c (<I >w</I><SUB>1</SUB>, <I >w</I><SUB>2</SUB>, h).</P>
<P>我不知道怎么做啊…………</P>