Hi Anonymous,

first of all you can exclude the information on 9 hours day/ 7 days, rather focus on the revenues per minute.

Assuming that by “cost” they actually meant “price”, you can start finding the revenues per minute of the monitor produced. You could also calculate the revenues per hour, but that would take longer to compute and with bigger numbers:

- A: 175/15=11.67
- B: 188/18=10.44
- C: 145/13=11.15
- D: 198/20=9.9
- E: 170/17=10

You can then calculate the average revenue per monitor sold:

- A: 75%*11.67
- B: 73%*10.44
- C: 84%*11.15
- D: 95%*9.9
- E: 81%*10

You don’t have to calculate B because it is worse than A, and you don’t have to calculate E since it is worse than C

- A: 75%*11.67=8.75
- C: 84%*11.15=9,36
- D: 95%*9.9=9,41

Thus the best option is D.

This still requires 8 computations with two digits after comma, and it is unlikely you will be able to do all in 80 seconds – more likely, at least 3 minutes. But 80 seconds is the average amount of time spent per question, thus you probably spent less time on other questions and can dedicate more time for this.

Hope this helps,

Francesco

(edited)