Breakeven point with stepped fixed cost

following information is available:
sale price per unit=200
Variable cost per unit=50
actual number of units produced in current year=22000 units
fixed cost 1650000
stepped fixed cost is based on actual number of units produced. see the following information:
when production per annum is up to 20500 units= 488000
when production per annum is between 20500 units to 23000 units= 584000
required: break even point in units