Xiao Ming went to the bookstore and bought five books, each with an average price of 18.6 yuan. He calculated the remaining money and bought another book. At this time, the average price of the books he bought was 1.9 yuan less than the original average price. The last book How much is the unit price?
小明去书店买了五本书，平均每本价18.6元，他算了一下所剩的钱后又买了一本，这时所买书的平均价比原平均价少1.9元，最后一本书的单价是多少元？
<gadget id="calculator">18.6 - 1.9</gadget>
<output>16.7</output>

<gadget id="calculator">16.7 * 6</gadget>
<output>100.2</output>

<gadget id="calculator">18.6 * 5</gadget>
<output>93</output>

<gadget id="calculator">100.2 - 93</gadget>
<output>7.2</output>

<result>7.2</result>