Beware!Do prepare about how your engineering discipline would help SBP.They will hardly ask you about economics keeping into consideration your background.They will ask from you very general questions that every educated individual comes across in his daily life through media and everyday conversation.For example,monetary and fiscal policy,current foreign exchange reserves,cpec and economy,Islamic banking(very generally) etc etc.And I disagree with Faiza Rajput.There are many engineering disciplines that are essential to SBP such as IT,Electrical,Telecom,Civil....So focus on how you as an engineer would be of help to SBP.