A block of mass m = 0.19 kg is set against a spring with a spring constant of k1 = 520 N/m which has been compressed by a distance of 0.1 m. Some distance in front of it, along a frictionless surface, is another spring with a spring constant of k2 = 247 N/m.

Now assume that the surface is rough (that is, not frictionless). You perform the experiment and observe that the second spring only compresses a distance d2/2. How much energy, in joules, was lost to friction?