A machine shop produces parts for the automobile industry, and one part has a design specification of 4.000 inches in length with a tolerance of ± 0.003 inches. The machining center operator making the part checks the output of each piece, and after 20 pieces, she finds the average part length to be 4.001 inches with a σ = 0.002 inches. 

a. What is the capability index for this part? 

b. Is the current process capable?