ValeriiGo: After wC13 bB13 is mistake, because all black stones are dead.
If bC14 then wA14, bA13, wD13 or wC12 and after bB13 some black stones are alive.
Ivan Detkov: Right, I guess this is why the task is "White to play", not "White to kill". There is nothing to correct here.
After C13 C14 A14 A13, D13 works too