For the normal distribution of burning times of electric light bulbs, with a mean equal to 1200

Question:

For the normal of burning times of electric light bulbs, with a mean equal to 1200 hours and a standard deviation equal to 120 hours, what burning time is identified with the
(a) Upper 50 percent?
(b) Lower 75 percent?
(c) Lower 1 percent?
(d) Middle 90 percent?
Distribution
The word "distribution" has several meanings in the financial world, most of them pertaining to the payment of assets from a fund, account, or individual security to an investor or beneficiary. Retirement account distributions are among the most...