प्रत्येक राउंड में 10 नये प्रश्न प्रश्न : ( 4 of 10 ) Karen can finish a work in 20 days. Lisa can finish the same work in 21 days while Nancy can finish the work in 22 days. How long will it take to finish it if they work together? (A) 21 days (B) 15.75 days (C) 12 654/661 days or 12.989 days (D) 6 654/661 days or 6.989 days