Are you intelligent enough to answer these? Part 2

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Hi guys. Let's check your iq. I'll wait for your answers. This is part 2 so it will start at number 6 6. What occurs once in every minute, twice in every moment, yet never in a thousands of years? 7. I an a seller of watermelon. My 1st customer bought half of the total watermelon and half watermelon. My 2nd customer bought half of the remaining watermelon and half watermelon. And my 3rd customer bought half of the remaining watermelon and half watermelon making my watermelons soldout. How many watermelons did I sell? 8. What is black when you buy it, red when you use it and gray when you throw it away? 9. A chemist guy and a mathematician lady had named their son "iron59" based on the jobs of the two. Translate the name into normal name. 10. A magic rectangular belt always shrinks its length to 1/2 and its width to 1/3 whenever its owner wishes something. After 3 wishes, its surface area was 4cm^2. What was the original length if the original width was 9cm?