For the reaction `A(aq)hArrB(aq)+2C(aq) K_C` at `25^@` is `4xx10^(-19)` Concentration of B in a solution that had originally C and B concentration of 0.1 M and 0.03 M respectively is :
A. 0.03 M
B. `7.5xx10^(-12) M`
C. `7.5xx10^(-15) M`
D. `7.5xx10^(-18) M`