In a reverse osmosis system, the water can be cooled using one of two systems: a single-pass heat exchanger or a closed-loop heat exchange system.

The single-pass system, good for 3 years, requires a small chiller costing $920 plus stainless steel tubing, fittings, etc., costing $360. The cost of water, treatment charges, electricity, etc., will be $3.10 per hour.

The closed-loop system will have a useful life of 5 years, cost $3850 to buy, and will cost $1.28 per hour to operate.

The salvage values are negligible. The company's MARR is 10%.

What is the minimum number of hours per year that the cooling system must be used in order to justify purchase of the closed-loop system? (Round your answer to a whole number of hours - no decimal places)