Algorithm to find most +EV in NETpoints Cash Giveaways

[fluorescenthippo]

So basically there is a weekly, biweekly, and monthly draw. The monthly draw costs 5 times more Epoints than the weekly draw but there is 6 times as much to win. Cleary this would be most +EV. however, there are usually far more entries in the monthly draws making your chances to win less likely.

anyone know the best way to figure out where to put your entries?