5. [Grade by Reader] Suppose you are conducting a quality control test on a manufacturing process that produces bolts. The length of these bolts follows a normal distribution with an unknown mean and a known standard deviation of 2 millimeters. We want to decide if = 3 (decision d0) or = 4 (decision d1) based on given 25 samples. If we estimate = 3 when actual = 4, the repair cost of each unit is $4. On the other hand, if we estimate = 4 when actual = 3, the repair cost of each unit is $8. Find the optimal decision rule for using the binary search