A Uranium Ore Contains 0

A Uranium ore contains 0.250 g of ²⁰⁶Pb per gram of Uranium. Assuming all of the lead was produced by decay of ²³⁸U (t_1/2 = 4.5×10⁹ years) , what is the age of the rock?

A) 4.4×10 ^{- 11} years
B) 8.1×10⁸ years
C) 1.9×10⁹ years
D) 3.2×10⁹ years
E) 9.0×10⁹ years