9. Plastic sheeting produced by a machine must be periodically monitored for possible fluctuations in thickness. Uncontrollable variation in the viscosity of the liquid mold products some variation in thickness. Based on experience with a great many samples, when the machine is working well, an observation on thickness has a normal distribution with standard deviation exceeded 1.36 mm. Sample of 20 thickness measurements are collected regularly. The value of the sample standard deviation 1.4mm signals concern about the product. Find the probability that the next sample will signal concern about the product. I