(1)    General. Rates determined under this chapter shall not be excessive, inadequate or unfairly discriminatory.

   (2)   Excessiveness. Rates determined under this chapter are not excessive merely because a reasonable margin is allowed for a profit.

   (3)   Adequacy. The commissioner shall approve a minimum adequate pure premium for each classification under which worker’s compensation insurance is written. No insurer writing any insurance specified under s. 626.03 may use a pure premium less than that approved by the commissioner.