Twice as Likely

In a large running club, 50% of members followed no structured plan, 35% followed a light plan and 15% followed an intensive plan to prepare for this year's marathon. Runners on the intensive plan are twice as likely to qualify for the Boston Marathon as runners on the light plan, and runners on the light plan are in turn twice as likely to qualify as runners with no plan.

You meet a club member who qualified. What is the probability that they followed the intensive plan? Give an exact fraction.