Mass collides with spring and mass

[NRasmus1]

A block of mass m1=1.60kg initially moving to the right with a speed of +4.00m/s on a frictionless horizontal track collides with a spring attached to a second block of mass m2=2.10kg initially moving to the left with a speed of -2.50m/s. The spring constant is 600N/m. At the instant block 1 is moving to the right with a speed of +3.00m/s, determine the velocity of block 2. Determine the distance the spring is compressed at that instant.

KE=1/2mv^2
Elastic PE=1/2Kx^2
Fp=Kx
Fs=-Kx

I'm going to start with conservation of energy, but this is too complex of a system for me to even begin. A step by step of how to set up this equation would be most helpful. Thank you all for your help!

 

[Xisune]

Try conservation of momentum.

 

[azizlwl]

Use both conservation of energy and comservation of momentum to get 2 equations for the 2 unknowns.