The formula to find weight would be density multiplied by volume. In this question, you are given the volume (3.25inch3), the density (0.242 g/cm3). Since the unit used in the volume and density is different, we need to convert it. The calculation would be:
weight = density * volume
weight = 3.25inch3 * (16.39 cm3/inch3) * (0.242 g/cm3)= 12.89 grams