A supermarket employee wants to construct an open-top box from a 24 by 36 inch piece of cardboard. To do this the employee plans to cut out squares of equal size from the four corners so the four...

A supermarket employee wants to construct an open-top box from a
 24 by 36 inch piece of cardboard. To do this the employee plans to cut
 out squares of equal size from the four corners so the four sides can be
 bent upwards. What size should the squares be in order to
 create a box with the largest possible volume?
 Round answer to 1 decimal place.