Balancing defect reactions:

Here is a defect reaction for $CaC{l}_2$ in NaCl :

$CaC{l}_2{?}^{\text{N}\text{a}\text{C}\text{l}},V_{Na}^{\text{'}}+Ca{?}_{Na}+2C{l}_{Cl}$

a$.$ Which compound is the "dopant"?

b$.$ Which compound is the "host"?

c$.$ Is mass balance maintained?

d$.$ What is the "site relation"?

e$.$ Is the defect reaction "electrically neutral"? Explain.