Why did the teachers delete 80% of my answers??? Most of them were right? I dont get it and i lost 200 points

Aproduction line has three machines a, b, and c, with reliabilities of .96, .86, and .85, respectively. the machines are arranged so that if one breaks down, the others must shut down. engineers are weighing two alternative designs for increasing the line’s reliability. plan 1 involves adding an identical backup line, and plan 2 involves providing a backup for each machine. in either case, three machines (a, b, and c) would be used with reliabilities equal to the original three. a. compute overall system reliability under plan 1. (round your intermediate calculations and final answer to 4 decimal places.) reliability b. compute overall system reliability under plan 2. (round your intermediate calculations and final answer to 4 decimal places.) reliability c. which plan will provide the higher reliability? plan2plan1

During the month of march 2017, weimar world, a tax-preparation service, had the following transactions. * billed $496,000 in revenues on credit * received $164,000 from customers' accounts receivable * incurred expenses of $194,000 but only paid $87,700 cash for these expenses * prepaid $32,220 for computer services to be used next month what was the company's accrual basis net income for the month? select one: a. $302,000 b. $264,080 c. $ 41,860 d. $408,300 e. none of the above

Russell's study compared gpa of those students who volunteered for academic study skills training and those who did not elect to take the training. he found that those who had the training also had higher gpa. with which validity threat should russell be most concerned?