Driving Tesuji Problem 2 / Attempts

Alex's Attempt  

This one's much more complicated than the last one. Here's the best thing I can figure out. White will sacrifice the marked stone, but she's threatening to save the rest of her stones, in which case Black's corner is in big trouble. Black can't play a because...

Alex's Attempt (Black smarter)  

Now Black's corner is okay, because the marked white stones will be captured, but the rest of White's stones will be okay. White will continue at a if the ladder works, and probably b if it doesn't. White c also threatens to capture Black's stones, but it looks to me like Black will win the capturing race by one move, as long as he responds.