A piece of elastic is attached to two nails on a flat board, as shown in the picture, with a button attached to the midpoint of the elastic. The nails are 5 cm apart. You stretch the elastic by pulling the button along the board in a direction that is perpendicular to the line between the nails. 5cm~ A. Find an equation that relates the total length of the elastic x to the distance y that the button has moved. B. You pull the button at a constant 3 cm/sec. Find the rate at which the length of the elastic is increasing when it is 12 cm long.