Ionization energies of three hypothetical elements given below (in kJ/mole)

	I	II	III
X	122	340	1890
Y	99	931	1100
Z	118	1220	1652

Energy (in kJ/mole) required for the process $\mathrm{Z}\to$ ${\mathrm{Z}}^{2+}+2e^{-}$ will be: