$${(R_1 \times R_2) \parallel R_3 = \frac{3}{2}{}{\Omega},\quad (R_2 \times R_3) \parallel R_1 = \frac{5}{6}{}{\Omega},\quad (R_1 \times R_3) \parallel R_2 = \frac{4}{3}{}{\Omega}}$$