The experimental primary school should be four. Every student in the fifth grade buys a 15 yuan composition guidance book. It is known that there are 123 students in the fourth grade and 128 students in the fifth grade. How much does it cost to buy books for the two grades?
实验小学要为四．五年级的每一位学生购买一本15元的作文辅导书．已知四年级有123人，五年级有128人，两个年级买书要花多少钱？
<gadget id="calculator">123 + 128</gadget>
<output>251</output>

<gadget id="calculator">251 * 15</gadget>
<output>3_765</output>

<result>3_765</result>