$10-34$ Learning curve, incremental unit$-$time learning model. Assume the same information for Northern Defense as in Exercise $10-33,$ except that Northern Defense uses an $85\%$ incremental unit$-$time learning model as a basis for predicting direct manufacturing labor$-$hours. $($An $85\%$ learning curve means $b=-0\mathrm{.}234465.)$

Calculate the total variable costs of producing $2,3,$ and $4$ units.

If you solved Exercise $10-33,$ compare your cost predictions in the two exercises for $2$ and $4$ units. Why are the predictions different? How should Northern Defense decide which model it should use?