I'm having a bit of trouble in coming up with the solution for this question A hard disk manufacturing process desposites a thin coating of magnetic material on a plastic substrate. Empirical measurement has shown that the process introduces 20 defects per 15000cm squared. A disk pack contains 800cm squared of this material. A disk pack with one defect is marketable because the disk controller can compensate for one error by using a spare location. What is the percentage of marketable disk packs produced by this process?