A quality analyst is checking the process capability associated with the production of struts, specifically the amount of torque used to tighten a fastener. Twenty-five samples of size 4 have been taken. These were used to create X-bar and R charts. The values for these charts are as follows. The upper and lower control limits for the X-bar chart are 74.80 Nm and 72.37 Nm, respectively. X-bar is 73.58 Nm. R-bar is 1.6. The specification limits are 80Nm plus or minus 10. Calculate 6-sigma, Cp, and Cpk. interpret the values.