Two blocks have mass m and M $=4\mathrm{.}46$m$,$ re$-$

spectively. A light spring is attached to one

of them, and the blocks are pushed together,

compressing the spring between them. They

are secured, in this compressed state, by a

cord. They are then placed, at rest, on a hor$-$

izontal, frictionless surface. The cord holding

them together is burned, after which the block

of mass M moves to the right with a speed of

$1\mathrm{.}56$ m$/$s$.$

What is the speed of the block of mass m$?$