The following diagram shows the relationship between national income and the government's budget balance (BB). BB Surplus a 0 National income (Y) De ficit (a) Define the term 'budget balance[ ] (6) Describe the budgetary position at Yi[] c) Assume that full employment is achieved at 72, what is the size of the structural budget balance? (d) If national income remains at Y2, and the BB line does not shift what will happen to the level of national debt?[] (e) What determines the slope of the BB line?[ ] (f) What would cause the BB curve to shift downwards?[ ]