<image>There is a solar water heater in a school cafeteria, and the maximum water storage capacity of its tank is 1000 liters. Water is added to the empty tank, and without any water being released from the tank, the relationship between the water storage volume \( y \) (liters) in the tank and the uniform water filling time \( x \) (minutes) is shown in the diagram.
(1) Try to find the functional relation between \( y \) and \( x \);
(2) If the tank originally contains 400 liters of water, and water is added at the above rate for 15 minutes, can the tank be filled to its maximum capacity?

