Could you show me the steps? PLease and Thank you

Acircle has a circumference of 28.36 units what is the diameter of the circle

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?

Written as a simplified polynomial in standard form, what is the result when (2x+8)^2(2x+8) 2 is subtracted from 8x^2-38x 2 −3?