Anyone know the answer?

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

Rose bought a new hat when she was on vacation. the following formula describes the percent sales tax rose paid b=t-c/c

3.4a=57.8 what is the the value of a