Way to go, Bro. Here's the nuts and bolts for those WSU grads.

Rope=1/3 LB/FT
Hanging Wt.=Wt. Monkey
Banana=2 Oz./In.
Length Rope=Age Monkey
Monkey Wt.(Oz.)=Monkeys Moms Age
Monkey Age+Moms Age=30

(Monkey/2)+Banana=(Rope Wt.+Hanging Wt.)/4
Therefore, Monkey+4Banana=Rope Wt.

x=Monkeys Age
y=Moms Age

y=3x/2
x=30-y
Therefore, y=3(30-y)/2
y=18
x=12

Rope=12'
Wt. Rope=0.333(12)=3.99 Lbs=63.99 Oz

Substitute into above: 18 Oz + 4 Banana = 63.99 Oz

Banana=11.49 Oz
11.49 Oz / (2 Oz/In) = 5.75"