Are you kidding me? Just because it's got 576 CUDA doesn't mean jack sh*t. 16 ROPs is going to be no better than a GTX 650. 64GBps bandwidth?? Are we still in 2011? With an unoptimized game like BF4 which won't run well on my GT 640 DDR5 rev. 1 (in essence, after clock adjustments, a GTX 650), yes, it will be able to run BF4, but you're not going to have a good time.
Does your cousin have an OEM pc? Because that's the only reason he would have one in the first place. If you're trying to save money for BF4, buy an R9 270/270X or an older GTX 660. Honestly, you're not going to regret it if you're building. Even an older 7850 or 650 Ti Boost will cut it way better than that GTX 645 piece of junk. Funny it's got the GTX label, because it's inferior to the GT 645 it's replacing (which was a Fermi rebrand of the GTX 560 SE).