Four engine bolts are tightened on an automated assembly line by four separate machines. Each machine is set to apply the same torque, , to its respective bolt but applies an actual torque, Ti, that follows a normal distribution with mean and variance 2 (each machine has the same variance and the operations are independent of each other). The tightening is considered to be acceptable if the average torque, (T1 + T2 + T3 + T4)/4, is within 10% of . What is the probability of an acceptable tightening? (Express your answer in terms of (z).)

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