How to calculate equilibrium income given a certain level of unemployment?
this is how I've solved it :

(a) Y=C+I+G = 800+0.6 Y
    So Y = 2000

(b) With 400 as government expenditure, the new equilibrium income will be 2500. So the increase in the income is 500.

(c) I think this will be solved using Okun's law ut-ut-1=0.4(gyt-3%). But I'm not sure how to proceed.