Volleyballs are 24 yuan each, and basketballs are 28 yuan each. Teacher Wang went to the store and bought 13 volleyballs and 12 basketballs. Based on the above information, please propose two mathematical problems and answer them in parallel.
排球每个24元，篮球每个28元．王老师去商店买了13个排球和12个篮球．请你根据以上信息，提出两个数学问题，并列式解答．
<gadget id="calculator">28 * 12</gadget>
<output>336</output>

<gadget id="calculator">24 * 13</gadget>
<output>312</output>

<gadget id="calculator">336 - 312</gadget>
<output>24</output>

<result>24</result>