A light spring of constant 155 N/m rests vertically on the bottom of a large beaker of water. A 4.31 kg block of wood of density 623 Kg/m³ is connected to the top of the spring and the block-spring system is allowed to come to static equalibrium. what is the elongation of the spring? The acceleration of gravity is 9.8 m/s². answer in units of cm.