**Answer:**

The probability that during a year, you can avoid catastrophe with at least one working drive is 0.9975

The probability that during a year, you can avoid catastrophe with at least one working drive is 0.999875

**Step-by-step explanation:**

**There is a 5% rate of disk drive failure in a year**

**So, probability of failure q = 0.05**

**Since the sum of probabilities = 1**

**So, probability of success p= 1-0.05**

** =0.95**

**Part a :** all your computer data is stored on a hard disk drive with a copy stored on a second hard disk drive

So, n =2

**We are required to find what is the probability that during a year, you can avoid catastrophe with at least one working drive**

**So, he probability that during a year, you can avoid catastrophe with at least one working drive :**

**Hence the probability that during a year, you can avoid catastrophe with at least one working drive is 0.9975**

**Part b :** If copies of all your computer data are stored on three three independent hard disk drives, what is the probability that during a year, you can avoid catastrophe with at least one working drive?

**Since there are 3 copies so, n =3**

**So, the probability that during a year, you can avoid catastrophe with at least one working drive:**

**Hence the probability that during a year, you can avoid catastrophe with at least one working drive is 0.999875**