The shop buys a batch of notebooks, each of which costs 1 yuan. If it is sold at 80% of the price, it can get 20% of the profit. Now, the cost of the notebooks is reduced, and they can still get 50% of the profit if they are sold at 70% of the original price. How much is the purchase price of this kind of book now?
商店购进一批本子，每本1元，若按定价的80%出售，能获得20%的利润，现在，本子的成本降低，按原定价的70%出售，仍能获得50%的利润，则现在这种本子进价每本几元？
<gadget id="calculator">20 / 100</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 * (1/5)</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">1 + (1/5)</gadget>
<output>6/5 = around 1.2</output>

<gadget id="calculator">80 / 100</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(6/5) / (4/5)</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">70 / 100</gadget>
<output>7/10 = around 0.7</output>

<gadget id="calculator">(3/2) * (7/10)</gadget>
<output>21/20 = around 1.05</output>

<gadget id="calculator">50 / 100</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 + (1/2)</gadget>
<output>3/2 = around 1.5</output>

<gadget id="calculator">(21/20) / (3/2)</gadget>
<output>7/10 = around 0.7</output>

<result>7/10 = around 0.7</result>