16.4 would be the greatest and 15.6 would be the least due to 2.5% equaling 0.4 and adding and subtracting it from 16.
-- If two lines on a graph are parallel, then their slopes are equal.
-- If two lines on a graph are perpendicular, then their slopes are
negative reciprocals.
Maybe prime number considering that 11 has no other factors. Hope I helped