Two Rockets, a and B, Approach Each Other as Shown

Two rockets, A and B, approach each other as shown in the figure. A travels to the right at 0.7c while B travels to the left at 0.8c. Both speed measurements are made relative to an inertial observer.
-Determine the ratio of the kinetic energy of rocket B to its rest energy.

A) 0.80
B) 0.67
C) 0.54
D) 0.33
E) 0.25