brief后必须附详细说明吗，都包括哪些

老师，IBD和R&D分别代表什么意思？

老师您好！这道题说市场由三家公司构成，但完全竞争市场不是有很多卖家吗？是不是有矛盾？

老师您好！请问，这里用 ATC=MC 算出 Q=8 后，如果代入 P=93-1.5Q，算出 P=81 ，这个价格表示什么意思呢？

Bill Fence, CFA, supervises a group of research analysts, none of whom have earned the CFA designation or are CFA candidates. On several occasions he has attempted to get his firm to adopt a compliance system to ensure that applicable laws and regulations are followed. However, the firm's principals have never adopted his recommendations. Fence should most appropriately: A resign from the firm, because no other alternative will keep him in compliance with the Code and Standards. B decline in writing to accept supervisory responsibility until reasonable compliance procedures are adopted. C take no further action, because by encouraging his firm to adopt a compliance system he has fulfilled his obligations under the Code and Standards. B选项中的decline in 怎么理解？是减少的意思吗？ B选项整个句子的含义让我蒙了

老师，这两道题如何计算？

您好，我想问一下关于liquidity risk的问题，我不记得是哪个reading里的了。所以liquidity risk可以显示在quoted price和实际交易价格差距大，并且demand少？还是什么coupon rate高？什么的不记得了。能不能帮我总结一下这个，谢谢！

cpr在第几个月没听懂，357个月是360个月过去3个月，在第四个月，这没听懂，请解答，谢谢

里面用记号笔标记的部分对应的分母变大的公式是什么？？？？？

里面用记号笔标记的部分对应的分母变大的公式是什么？？？？？