**Source:**Asked to me by Ankush Jain (CSE IITB 2011, Morgan Stanley Quant Associate). He took it from Algorithms Design book by Tardos and Kleinberg

**Problem:**

__Easy case:__

You’re trying to buy equipments whose costs are

__appreciating. Item__*i*appreciates at a rate of*r_i*> 1 per month, starting from $100, so if you buy it*t*months from now you will pay*100*((r_i)^t)*. If
you can only buy one item per month, what is the optimal order in which to buy them?

__Difficult case:__

You’re trying to sell equipments whose costs are depreciating. Item

*i*depreciates at a rate of*r_i*< 1 per month, starting from $100, so if you sell it*t*months from now you will get*100*((r_i)^t)*. If
you can only sell one item per month, what is the optimal order in which to sell them?