A shopper bought 7 ears of corn and 6 pounds of bananas and paid $5.15. At the same store, another shopper bought 4 ears of corn and 1 pound of bananas and paid $1.85 . What is the price of an ear of corn? Please help!

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