The school wants to buy 150 pine saplings, and the price is 15 yuan per gram. Now there is a discount, buy 4 and get one free. How much did the school spend on buying saplings?
学校要买150棵松树苗，每克售价15元，现在优惠，买4棵送一棵．学校买树苗一共花了多少钱？
<gadget id="calculator">4 + 1</gadget>
<output>5</output>

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

<gadget id="calculator">15 * (4/5) * 150</gadget>
<output>1_800</output>

<result>1_800</result>