Please help me answer this answer choice

Glenda makes an online purchase for picture frames for $12.95 each and formats of $5.89 each the site says it taxes paid by the customer or 6.5% of the total purchase price shipping charges are based on the

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?

Me i’m stuck on all these questions besides the two bottom ones