3) (30 pts.) Two spin 1/ 2 particles are in a box. The rst particle is an electron while the second particle has no charge, and therefore no magnetic moment. The box is inside a magnetic eld of magnitude BU in the +2: direction. At t = 0, the total spin of the box is measured, and the box is found to be in the Siam: : 0 state. Considering how the presence of the magnetic eld affects the time evolution of the spin states of the two particles, what is the earliest time (t > U) at which a measurement of the total spin of the box will yield 8mm: = 1 with 100% probability? (Food for thought: what happened to conservation of angular momentum?)