What Is the Sum of the Coefficients When the Following $\rightarrow$

Multiple Choice

What is the sum of the coefficients when the following chemical equation is balanced?
A Ca₃(PO₄) ₂(s) + B C(s) $\rightarrow$ C Ca₃P₂(s) + D CO(g)

A) 6
B) 12
C) 18
D) 20
E) none of the above