So the laptop that I was using randomly tuned off while I was doing my work...I thought it was on low battery si I charged it bug it's still not turning on. Can anyone please tell me what's wrong with it and how can I fix it?(I was just listening to music and it had some essay tabs open...).

The reliability of a hard-disk drive is typically described in terms of a quantity called mean time between failures (mtbf). although this quantity is called a “time,” the mtbf actually is measured in drive-hours per failure. if a system contains 1,000 disk drives, each of which has a 750,000-hour mtbf, which of the following best describes how often a drive failure will occur in that disk farm: once per thousand years, once per century, once per decade, once per year, once per month, once per week, once per day, once per hour, once per minute, or once per second?