A tomato vendor decides to switch who he buys his tomatoes for.  He sells 500 tomatoes a day.  He used to buy them for $.5 each but he gets a new vendor who sells them for $.4 each.  How much money does he save a week?
He buys 500*7=
<gadget id="calculator">500*7</gadget>
<output>3_500</output>
3500.
He used to pay 3500*.5=$
<gadget id="calculator">3500*.5</gadget>
<output>1_750</output>
1750.
He now pays 3500*.4=$
<gadget id="calculator">3500*.4</gadget>
<output>1_400</output>
1400.
So he saves 1750-1400=$
<gadget id="calculator">1750-1400</gadget>
<output>350</output>
350.

<result>350</result>