hello..
2006,
q21> option b bcoz the allocation (3,3) and (7,2) lies on the 45degree line.. so it is pareto efficient however not competitive .. since competitive allocation for the economy is x1=[5,10], y1=5 while x2=10-x1 and y2=0
q22> option a (mentioned above)
q23> option b ( as at all other price ratios markets will not clear)
for 2005,
refer the following link:
http://discussion-forum.2150183.n2.nabble.com/dse2005-td5190800.html#a5190800
:)