All of your 3 possible percentages are wrong.
The yield will be the median average of all 5 lasers based off damage.
The math is a bit difficult, but I will try to explain it.
You have 5 lasers:
22dps 90%
20dps 87%
24dps 80%
18dps 85%
16dps 70%
if you add up the DPS (22+20+24+18+16=100) Then you take each individual dps and divide the total by the individual so 22 dps would be 22/100 = .22 or 22%, then you multiply the efficiency by this number, so 22% of 90%, you get 19.8%
Do that for all of them:
22dps 90% 19.8%
20dps 87% 17.4%
24dps 80% 19.2%
18dps 85% 15.3%
16dps 70% 11.2%
Add them all up 82.9% is the final efficiency. This is assuming ALL lasers are hitting the asteroid for an EQUAL time (and in most cases it is close enough)
And don't forget, there is always refinery tax, usually between 20% in the outer systems (YUCK) and .5% in the core, 20% reduces what you get from 82.9% to 66.3% while the 0.5% only takes it to 82.5, a very big difference.
So TLDR, it is dps AND efficiency averaged out to get the actual % of ore off the rock.