The school needs to buy a tutorial book for each student in the third and fourth grades at a price of 18 yuan. It is known that there are 145 students in the third grade and 155 students in the fourth grade. How much is the total cost for the two grades?
学校要为三、四年级的学生每人买一本价格为18元的辅导书，已知三年级有145人、四年级有155人，两个年级一共需要多少元？
<gadget id="calculator">145 + 155</gadget>
<output>300</output>

<gadget id="calculator">300 * 18</gadget>
<output>5_400</output>

<result>5_400</result>