Need correct answer with detailed calculation

A paper clip machine makes 4,000,000 paper clips each month. The machinist measures every 10,000th paper clip to be sure the machine is still set correctly. When the machine is set correctly, the measurements follow a normal distribution. The machinist uses only Test 1 (one value more than three standard deviations from the mean). Suppose the machine remains set correctly for a month. How many times would you expect the operator to stop production anyway?