Aproduction line is in-control, centered and the quality characteristic of interest is normally distributed. the process capability ratio cpk = 0.90 and the specifications limits (lsl, usl) are (86, 130). (a) how many process standard deviations separate the process mean from the upper specification limit? (b) what is the dpmo falling below the lower specification limit? (c) what is the sigma level for the process? (d) calculate the zbench and the sigma quality level (sql) for the process? (e) by how much would the process standard deviation have to be reduced to have a true six sigma (6σ) process?