$r = \frac{1}{2}(1.5)$

$r = \frac{3}{4} ~ \text{in.}$

$R = r + \frac{1}{4}$

$R = 1 ~ \text{in.}$

$V = A_bh$

$V = \pi (R^2 - r^2)h$

$V = \pi [ \, (\frac{1}{12})^2 - (\frac{3/4}{12})^2 \, ](20)$

$V = \frac{35}{576}\pi ~ \text{in.}^3$

$W = \gamma V$

$W = 520(\frac{35}{576}\pi)$

$W = 99.2656 ~ \text{lb.}$ *answer*