Coring was performed for the Wilcox Sand of Altair Field at a depth of 8270 ft. One core plug of 1-inch diameter and 2.5 inches length was cut from the whole core for the purpose of the porosity measurement. The core was extracted, dried, and then weighed. The dry weight was 68.01 g. The core was then put under vacuum and brine was introduced to fully saturate the core. The saturated core weighed 74.30 g. The density of the brine was 1.03 g/cm3. From the data given, determine the porosity of the rock. Is it an effective porosity or a total porosity? Why?