Mining a charged black hole and the third law of black hole thermodynamics

We consider the rate at which energy can be extracted from a charged black hole using the mining process developed by Unruh and Wald. It is shown that for a Reissner-Nordström black hole the mining rate depends on the mass of the hole (unlike in the Schwarzschild case) and goes to zero asT^BH 0. We also argue that it is impossible to achieveT_BH=0 in a finite time by mining.