A roof drains into a gutter, which feeds into a downspout with a square cross section (4 in. $x$ 4 in.). The discharge end of the downspout is $12 \mathrm{ft}$ below the entrance and terminates in a $90^{\circ}$ mitered (one weld) elbow. The downspout is made of smooth sheet metal.

(a) What is the capacity of the downspout, in gpm?

(b) What would the capacity be if there were no elbow at the bottom?