Three thermochemical equations are given below

$\text{ (a) }\underset{(\text{ graphite) }}{\mathrm{C}}+\underset{\left(g\right)}{O_2}\to C{O}_2,\mathrm{\Delta }{H}^0=x \mathrm{KJ}/\text{ mole }$

$\text{ (b) }\underset{\text{ (graphite) }}{C}+\frac{1}{2}{\mathrm{O}}_{\left(g\right)}\to \underset{\left(g\right)}{CO},\mathrm{\Delta }{H}^0=y KJ/\text{ mole }$

$\left(c\right) \underset{\left(g\right)}{\mathrm{CO}}+\frac{1}{2}\underset{\left(g\right)}{O_2}\to \underset{\left(g\right)}{C{O}_2},\mathrm{\Delta }{H}^0=z KJ/\text{ mole }$

Based on above equations find out which of the relationship given below is correct?