A Saturated Sodium Carbonate Solution at 0 ^$\circ$ C Contains 7

A saturated sodium carbonate solution at 0 ^$\circ$ C contains 7.1 g of dissolved sodium carbonate per 100. mL of solution. The solubility product constant for sodium carbonate at this temperature is

A) 1.2.
B) 0.30.
C) 3.0 * 10^-4.
D) 0.90.
E) 1.2 * 10^-3.