Logic Problem for GoT

[maurile]

Before you there are two boxes, one white and one black. Each box contains money; one has twice as much as the other. You may choose either box and keep whatever money is inside.

You choose the white box and find $100 in it.

You are now given the option of switching. You may either keep the contents of the white box, or you may instead opt for the contents of the black box.

What's the EV of switching?