Mr. Smith drove for 45 minutes at a speed of 40 km/h. He stopped for 15 minutes for a coffee break and then he drove for 2 hours at a speed of 75 km/h. What was his average speed for the entire journey?

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?