semiconductor quatum well find band gap question

brocq_18

Hiya, been given this question which I am having problems with.

Semi conductor quatum well structure contains a 100A thick layer of GaAs between thick AlGaAs layers. Find the band gap for the structure, where GaAs has the following parameters; conduction band effective mass 0.067 me, heavy hole mass 0.45me, band gap 1.519 eV. Assume conduction and valence bands offset at the GaAs/AlGaAs interfaces are infinite.

I have gotten that electron energy at the lowest level of conduction band is =Ec+(hbar(2)k(2))/2m0me. How do i progress from here?

Thanks