Helibeb Limited buys and sells brown coarse sand in the course of its business.

At the start of last month, Helibeb had an inventory of brown coarse sand valued at 5406 at cost

During last month, Helibeb bought coarse brown sand costing 6000

At the end of last month, Helibeb had an inventory of brown coarse sand valued at 4500

Note: No brown coarse sand was written off or written down as damaged or unsaleable in the course of last month.

How much was Helibeb's cost of inventory of brown coarse sand last month?