A set of 10 new questions in each round. Question: ( 1 of 10 ) If Robert can finish the work in 26 days and David can finish the same work in 42 days, then in how many days both can finish the work together? (A) 16 1/17 days or 16.059 days (B) 34 days (C) 68 days (D) 32 1/17 days or 32.059 days