1 pound (lb) = 453.592 g
Therefore, 5.4 pounds will be equivalent to 5.4 × 453.592 = 2449.397 g
1 cubic inch = 16.387 cubic cm
Therefore, 13.6 cubic inches will be equivalent to 13.6 × 16.387 = 222.863 cm³
Density is given by mass divided by volume
Thus density = 2449.397 g / 222.863 cm³
= 10.991 g/cm³