A student draws a free-body force diagram of a box moving at constant velocity. The diagram shows 80 N right, 50 N left and 200 N down. Two forces have been omitted. Which pair must be added?
30 N30\ \mathrm{N}30 N right and 200 N200\ \mathrm{N}200 N up
130 N130\ \mathrm{N}130 N left and 200 N200\ \mathrm{N}200 N up
30 N30\ \mathrm{N}30 N left and 200 N200\ \mathrm{N}200 N up
130 N130\ \mathrm{N}130 N right and 200 N200\ \mathrm{N}200 N down