1.15 A sandstone core sample (d=1.90 cm and L=3.20 cm) is satu- rated with a brine of 0.55-0 m resistivity. The core was desaturated in steps, and the following resistances were meas- ured at each saturation. Sw (fraction) (N) 1.000 521 0.900 0.800 678 913 0.730 1,151 1,510 2,255 3,135 5,270 6,820 10,400 0.640 0.560 0.480 0.375 0.350 0.300 a. Estimate the rock porosity. -b. Determine the saturation exponent, n, of the rock.