A, B and C enter into partnership. A invests some money at the beginning, B invests double the amount after 6 months, and C invests thrice the amount after 8 months. If the annual gain be Rs.18000. A's share is? Choose the correct answer:
A) Rs.7500  B) Rs.7200  C) Rs.6000  D) Rs.5750  E) Rs.6750
x* 12 : 2x* 6: 3x* 4   1:1:1   1/3 * 18000= 
<gadget id="calculator">1/3 * 18000</gadget>
<output>6_000</output>
6000   ANSWER:Rs.6000
<result>C</result>
A, B and C enter into partnership. A invests some money at the beginning, B invests double the amount after 6 months, and C invests thrice the amount after 8 months. If the annual gain be Rs.18000. A's share is?