The successive ionization energies (IE) for an element A are as follows  
`A overset(IE_1)(rarr)A^(+) overset(IE_2)(rarr)A^(2+) overset(IE_3)(rarr) A^(3+) rarr ….`
If the `IE_1 and IE_3` values are `27 kJ mol^(-1)` and `51 kJ mol^(-1)` respectively, then the value of `IE_2` is ______`kJ mol^(-1)`. 

Options

A. 21
B. 33
C. 59
D. 63

Answer

B