When smart people make money, fools lose money.

(coin=1000) A few questions have been posted; choose one question to answer, and write the number and your answer in reply to my space. If correct, I will transfer the money directly to your space. Each person can only answer one question (please do not answer in the post, otherwise you will get nothing).\ a. A patch of grass grows at a constant rate, enough for 25 cows to eat for 20 days or 30 cows to eat for 10 days. How many days is it enough for 40 cows to eat? (Reward 10000)\ b. Person A takes 10 days to complete a section of road. After working 3 days, he fell seriously ill and his work efficiency dropped by 90%, continuing to work until completion when he recovered. How many days did Person A work in total? (Reward 5000)\ c. What is the remainder when 365 to the 666th power is divided by 9? (Reward 30000)(/coin)