The mathematical model for learning an assembly-line procedure needed for assembling one component of a manufactured item is where P is the proportion of correctly assembled components after n practice sessions. How many practice sessions are required to have at least 65% of the components correctly assembled within the given time period

I’m stuck on this equation, anyone got the answer?

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?

B. two events are dependent if the occurrence of one event changes to occurrence of the second event. true or false