The Imperial II strategy card allows the selection of option (a) where a player may qualify for any number of public objectives during the upcoming status phase. If both the "I now spend 6 trade goods" and the "I now spend 12 trade goods" objectives are available, how many trade goods must the player spend?

I would think 18 (6 + 12), but I can see how someone might also think that paying 12 goods in effect qualifies for both objectives simultaneously.

Whatever the answer, I expect this would also apply for the spending of influence/resource type "I now spend..." objective cards.

So, in theory, you could spend 12 trade goods and 20 influence and qualify for a whopping boatload of points, depending on the Stage 1s and Stage 2s available.

Seren said:

You are correct, he must spend 18. The player can qualify for as many objectives as he likes, but he must qualify for each one individually.

I'm not sure how clear the actual rules are on this point, but in order to qualify for any objective, you must prove the statement on the card true at the moment you claim it. So "I now spend 6 trade goods" will only be true if you immediately spend 6 trade goods . Once spent on that, they cannot be spent on another card. In general, a single unit of currency cannot be spent on two different things, even simultaneously.