On balancing the given redox reaction, ${\text{aCr}}_{\text{2}}{\text{O}}_{\text{7}}^{\text{-2}}{\text{+bSO}}_{\text{3}}^{\text{-2}}{\text{+cH}}^{\text{+}}\to {\text{Cr}}^{\text{+3}}{\text{+SO}}_{\text{4}}^{\text{2-}}{\text{+H}}_{\text{2}}\text{O}$.  The coefficients a,b and c are found to be, respectively.