Circuit Element Question using Kirchoff's law

[Paymemoney]

Homework Statement

[PLAIN]http://img137.imageshack.us/img137/355/circuit2.png

Homework Equations

P=VI
P=I^2 R

V=IR

The Attempt at a Solution

The part a is all correct.
i_\wedge = 5A
i_o = 2A
v_o = 80V

This is what i have done in part b but it is not correct because P_delivered not equal to P_absorbed.

P_d = (50*7)+(20*40)
P_d = 1150W

P_a = (5^2*18)+(2^2*40)+(8*5)(20)
P_a = 1410W

I am not sure if the dependent voltage source is power absorbed or delivered.

Can somebody explain to me what have they done in the part b answers. For instance how did they get the values for i_g?
[PLAIN]http://img257.imageshack.us/img257/6798/circuit2answer.png

P.S

 

[danago]

I think you have mixed up which elements are absorbing power and which are delivering. The way i have always though about it (not that i need to think about it often, being a chemical engineering major haha) is that when current enters the positive terminal and leaves the negative terminal of an element, the element is absorbing power (and vice versa). Doing this gave me an answer of 4230W being absorbed and delivered in total.

It looks to me that i_g is obtained by a current balance.