A teacher can grade 20 papers during an uninterrupted planning period and 10 papers for each hour he spends at home grading. What function models the number of papers he can grade given that he has 2 uninterrupted planning periods and x full hours devoted to grading at home?
(A)20 + 2x (B)20x + 10 (C)40x + 10 (D)40 + 10x
D