Four identical bottles contain a certain amount of oil respectively, each bottle is weighed together with other bottles, and the kilograms are recorded as follows: 8, 9, 10, 11, 12, 13. It is known that the sum of the weights of the four empty bottles and the sum of the weights of the oil are prime numbers, how much oil is in the two heaviest bottles?
四只同样的瓶子内分别装有一定数量的油，每瓶和其他各瓶分别合称一次，记录千克数如下：8、9、10、11、12、13．已知四只空瓶的重量之和以及油的重量之和均为质数，求最重的两瓶内有多少油？
<gadget id="calculator">0.5 * 2</gadget>
<output>1</output>

<gadget id="calculator">13 - 1</gadget>
<output>12</output>

<result>12</result>