Please note the numbers may change from one question to another.

Topgun Records and several movie studios have decided to sign a revenue$-$sharing contract for CDs$.$ Each CD costs the studio $$2$ to produce. The CD will be sold to Topgun for $$4.$ Topgun in turn prices a CD at $$18$ and forecasts demand to be normally distributed, with a mean of $5,000$ and a standard deviation of $2,000.$ Any unsold CDs are discounted to $$1$ each, and all sell at this price. Topgun will share $35$ percent of the revenue with the studio, keeping the remaining for itself.

What is the unit underage cost for Topgun? Please carry two decimal places for your answer.