this week sadly its 0.0003 BTC/1MHs X11/24 hour, on average. each 280x give you 4.2 MHs, so 0.0003*4.2*$600=0.756 USD per day for each 280X card.
you need 100 280x to earn $75.6 USD per day before electricity cost, so getting a job at your local McDonalds is better than GPU mining X11 coins.

GPU mining is dead, don't do it if you didn't already invest in tons of equipments.

only back in december 2013, mining LTC with 280x had good profit.