How did you calculate the local skin friction coefficient

A reciprocating type ball-on-disc tribometer was used to measure the tribological behaviour of the thermally sprayed cobalt oxide coatings against the alumina (Ø 6.35 mm) counterface. After wear testing at high temperatures, the area of the wear tracks was 300 μm² measured by a white light microscope. The following parameters were used for sliding wear testing. Parameters Applied load (N) Sliding velocity (cm/s) Test frequency (Hz) Track length (mm) Total sliding cycles Total sliding distance (m) Values 10 3.14 1 10 2500 50 Determine the wear volume in mm³ that was removed during the sliding process and the specific wear rate (mm³/N.m.).