code: public double getValueAt(int k) {
      if (k < k_0) {
        return Double.POSITIVE_INFINITY;
      }
      return m * FastMath.log(k) + t;
    }
docs: Returns the function value of the approximation line at the specified k.
  
  @param k the value for which the function value of the approximation line
  should be returned
  @return the function value of the approximation line at the specified k