Hi, I just ordered 5 TH / s from Black Arrow 4 months contract for 12k USD, before paying I just want to ask you if anyone did it before and if you belive them?

This is my calculation to difficulty mining in BTC from March to July: If it would be true, this contract wil be in BE in month and next 3 months are ++

jump                           difficulty               Diff %
1 (on 2014/03/10)   4,583,606,945   + 23.7 %
2 (on 2014/03/22)   5,637,492,863   + 23.0 %
3 (on 2014/04/03)   6,895,940,103   + 22.3 %
4 (on 2014/04/15)   8,390,472,259   + 21.7 %
5 (on 2014/04/27)   10,155,944,787   + 21.0 %
6 (on 2014/05/09)   12,230,656,051   + 20.4 %
7 (on 2014/05/21)   14,656,427,398   + 19.8 %
8 (on 2014/06/02)   17,478,648,308   + 19.3 %
9 (on 2014/06/14)   20,746,283,038   + 18.7 %
10 (on 2014/06/26)   24,511,835,766   + 18.2 %
11 (on 2014/07/08)   28,831,271,812   + 17.6 %


What are yours opinions?

thank you