Nita and Gita sell goods worth Rs.3000 and Rs.4000 respectively. Gita calculates profit margin and Nita calculates actual profit percentage. What is the difference between the cost prices of the two cases if both claim to have a profit of 20%?(Profit margin is calculated on selling price while actual profit percentage is calculated on cost price)

1) Rs.700
2) Rs.600
3) Rs.500
4) Rs.800
5) None of these