(50 points) the manger of a sawmilll wants to find out what percentage of the boards that the mill produced are defective. which sampling method are likely to be biased? a). on 1 day, an hour after the sawmill begins production, 30 boards in a row are selected and examined. b). the manager selects 20 boards at random each day for 5 days and examines them. c). every 40th board produced over the course of 1 week is selected and examined. d). the manager sends an email to 20 customs who buy lumber from the mill, asking each how many of the boards they bought the past week were defective. results from the first 5 customers to respond are tallied.