Two identical fermionic particles with spin s 1/2 are placed in an infinite square well (r) 0, 0 x a such that one particle is in the single particle ground state and the other one is in the oo, otherwise' single particle first excited state. calculate the quantity k (x x2)2 where x1,x2 are the position operators of the two particles. make sure that the spin degree of freedom is taken into account explicitly. how would this quantity change if the two particles were distinguishable