Under 46 CFR §28.570, a vessel's righting arm curve must show a minimum area of how many foot-degrees between 30° and the lesser of 40° or the angle of downflooding?

Why C is correct

46 CFR §28.570(a)(6) requires a minimum area of 5.6 foot-degrees (0.030 meter-radians) under the righting arm curve between 30° and the lesser of 40° or the angle of downflooding. The 16.9 and 10.3 foot-degree values apply to different angle ranges under §28.570(a)(4) and (a)(5) respectively.