Assume that the total amount of commodities is 100 unit, and the cost of each commodity is also 100 unit.

The total cost of goods is100×100 =10000.

Then according to the profit of 30%, the price is 130, the sales rate is 70%, and the sales income is 130×70=9 100.

The remaining 30% is sold at half the price of 65, and the sales income is 65×30= 1950.

Total sales revenue is 9100+1950 =11050.

The profit is11050-10000 =1050.