This question needs an explanation and an answer. Please help! I need the extra points to get a 100 in the class!

(write as unit rate) 12 meters in 2.8 seconds =

Apinhole camera is made out of a light-tight box with a piece of film attached to one side and pinhole on the opposite side. the optimum diameter d(in millimeters) of the pinhole can be modeled by d=1.9[ (5.5 x 10^-4) l) ] ^1/2, where l is the length of the camera box (in millimeters). what is the optimum diameter for a pinhole camera if the camera box has a length of 10 centimeters

Math question.. plz me .. best answer all