A massless spring with spring constant kk is placed between a block of mass mm and a block of mass $3$m$3$m$.$ Initially the blocks are at rest on a frictionless surface and they are held together so that the spring between them is compressed by an amount DD from its equilibrium length. The blocks are then released and the spring pushes them off in opposite directions. between a block of mass mm and a block of mass $3$m$3$m$.$ Initially the blocks are at rest on a frictionless surface and they are held together so that the spring between them is compressed by an amount DD from its equilibrium length. The blocks are then released and the spring pushes them off in opposite directions.

Part A

Find the speeds of the two blocks when they detach from the spring.

Express your answers in terms of the variables DD$,$ kk and m