Calculating Magnetic Field from Spin Alignment Energy Difference

[tigert2004]

An electron is placed in a magnetic field B that is directed along a z axis. The energy difference between parallel and antiparallel alignments of the z component of the electron's spin magnetic moment with B is 4.50 10-25 J. What is the magnitude of B?

energy=Beh/4pim 4.5e-25 = B (1.6e-19)(6.626e-34)/ 4pi 9.109e-31

B=4.5e-25/9.27e-24

B=.0485 T
B =48.5 mT

But this seems to be wrong?

 

[tigert2004]

I have also tried -48.5mT but that is wrong also

 

[OlderDan]

Is it because the problem is giving youthe energy difference between the two alignments?