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百亿和十亿级别的企业研发投入总和1.76 万亿元，以6.39%的企业总数（378 家），占到全部研发投入的六成（64.94%）。。体育直播对此有专业解读
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I learned that for 4-SAT, if clause to variable ratio is more than 10, the generated problems become difficult to solve, and the likelihood of formula to be SAT or UNSAT is close to 50%. So I generated 3 types of formulas: