\(R_1 = \pi \times 10^{-6}\, \Omega, R_2 = 2 \times 10^{-6}\, \Omega, R_3 = \pi \times 10^{-6}\, \Omega\)
\(\frac{1}{{{R_{AB}}}}\,\, = \,\,\frac{1}{{\pi \,\, \times \,{{10}^{ - 6}}}}\,\, + \;\,\frac{1}{{2\,\, \times \,\,{{10}^{ - 6}}}}\,\, + \,\,\frac{1}{{\pi \,\, \times \,\,{{10}^{ - 6}}}}\)
\(\, = \,\,0.88\,\, \times \,\,{10^{ - 6}}\,ohm\).