The crates of weight 1490N will move with speed 2.2m/s at the top of a ramp that slopes downward at an angle 21.0^\circ. The ramp will exert a 533N force of kinetic friction on each crate, and the maximum force of static friction also has this value. At the bottom of the ramp, each crate will come to rest after compressing a spring a distance x. Each crate will move a total distance of 7.7m along the ramp; this distance includes x. Once stopped, a crate must not rebound back up the ramp. Calculate the maximum force constant of the spring k_max that can be used in order to meet the design criteria.