Answer
4.05 pounds
Work Step by Step
$weight = constant * radius^3$
radius = 2 inches, weight = 1.2 pounds
$w=k*r^3$
$1.2 = k*2^3$
$1.2 = 8k$
$1.2/8=8k/8$
$.15=k$
$w=.15r^3$
3 inch radius
$w=.15r^3$
$w=.15*3^3$
$w=.15*27$
$w=4.05$ pounds