The Yucca Mountain Repository in Nevada, Which Is Intended for the Long-Term

The Yucca Mountain repository in Nevada, which is intended for the long-term storage of nuclear waste, has long been mired in controversy. One ongoing concern is whether the stainless steel alloy containers could be corroded by salts such as calcium fluoride. If the calcium ion concentration in water inside Yucca Mountain is 1.25 $\times$ 10^-3 M, what is the maximum possible concentration of fluoride ion in this water? Assume calcium fluoride K_sp = 2.2 $\times$ 10^-10 at the temperatures inside the nuclear waste depository.

A) 1.3 $\times$ 10^-3 M
B) 2.5 $\times$ 10^-3 M
C) 1.8 $\times$ 10^-7 M
D) 4.2 $\times$ 10^-4 M
E) 2.1 $\times$ 10^-4 M