mandatory pentafecta in race 12-pool will be over $1mil and probably closer to $2mil
I might key #12 Dublin Dasher on top and play a bunch of numpers underneath.....bu t obviously one must narrow it down somewhere or its gets too expensive
good luck 
If you keyed a horse on top, and two horses for second, and 7 horses for 3rd, 4th, and 5th, it's a $48 ticket, but even with that, you're still totally eliminating five horses which makes it risky.