I see the page is unclear.
Basically, the important value is min(Base, Intent). If you work together, the value is min(sum(Bases), sum(Intents)).
So, in your example, add up your skill values - together, you have Control 4-5 and Mind 17. Since Control is the lower value, use that (4 or 5). Assuming it's 4, so the time required is 24*24/4 = 144 hours.
You may want to check what other things you can do to reduce the ritual time. :-)
