The Besty Limited company used regression analysis to predict the annual cost of indirect materials. The results were as follows:

Indirect Materials Cost Explained by Units Produced

      Constant (a)                                                                 N$ 21 890

      Standard error of Y estimate                                         N$ 4 560

      r2                                                                                        0.7832

      Number of observations                                                           22

      X coefficient(s) (b)                                                               11.75

      Standard error of coefficient(s)                                         2.1876

What is the linear cost function?