An archaeologist discovers a piece of a ceramic plate. She knows that if the plate is from the third century it was probably a regular 16-gon, but if it was from the twelfth century it was probably a regular 18-gon. If one of the angles on the piece she found is 160o , from which century did the plate most likely originate? Why?

Assume that there is a 11% rate of disk drive failure in a year. a. if all your computer data is stored on a hard disk drive with a copy stored on a second hard disk drive, what is the probability that during a year, you can avoid catastrophe with at least one working drive? b. if copies of all your computer data are stored on four independent hard disk drives, what is the probability that during a year, you can avoid catastrophe with at least one working drive?