Goods costing

All the sales made by a retailer are for cash , and her sales prices are fixed by doubling cost. Details recorded of her transactions for September 2006 are as follows.
1 sept inventories $40,000
30thsept purchases for month $60,000
cash banked for sales for month $95000
inventories $50,000
Which two of the following conclusions could separately be drawn from this information?
1. $5000 cash has been stolen from the sales revenue prior to banking.
2. Goods costing $5000 has been stolen
3. Goods costing $2,500 have been stolen
4. Some good costing $2,500 had been sold at cost price.
The answer is 1 and 3 sir..i understand the fact that oi + p -ci = cos
so cos is 50,000.. i dont get how at the back they have given 100,000 (50,000X2)
dont get the logic ? 50,000-95000=45000 not 5000? what if i use cos 95000? so the closing inventory is coming 50000