Dear Tutor,

Could you help me with the following task?

Jack Welch, former CEO of General Electric, famously used a 20-70-10 "stacked-ranking" system for his managers. The top 20% received bonuses and stock options, the middle 70% received no bonuses, and the bottom 10% was fired. Assume that the performance of managers can be described by a normal distribution.

(a) How many standard deviations above the mean would a manager need to be to earn a bonus?

(b) How many standard deviations below the mean would a manager need to be to get fired?

Any help would be highly appreciated!

Thank you.