Ineed to find the lcd but i don’t know how i need .

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

What are the values of each variable in the diagram below?

If each bricks costs and he can only buy one brick how much will it cost him to get the material to put around the outside of his garden?