Code refactoring homework?

Question

This is the code that I have to refactor for my homework:

if (state == TEXAS) {
    rate = TX_RATE;
    amt = base * TX_RATE;
    calc = 2 * basis(amt) + extra(amt) * 1.05;
} else if ((state == OHIO) || (state == MAINE)) {
    rate = (state == OHIO) ? OH_RATE : MN_RATE;
    amt = base * rate;
    calc = 2 * basis(amt) + extra(amt) * 1.05;
    if (state == OHIO)
        points = 2;
} else {
    rate = 1;
    amt = base;
    calc = 2 * basis(amt) + extra(amt) * 1.05;
}

I have done something like this

if (state == TEXAS) {
    rate = TX_RATE;
    calculation(rate);
} 
else if ((state == OHIO) || (state == MAINE))
    {
rate = (state == OHIO) ? OH_RATE : MN_RATE;

calculation(rate);

if (state == OHIO)
    points = 2;
}

else {
    rate = 1;
    calculation(rate);
}

function calculation(rate)
{
    amt = base * rate;
    calc = 2 * basis(amt) + extra(amt) * 1.05;
}

How could I have done better?
Edit i have done code edit amt = base * rate;

Answer 1

class State {
private :
  double taxRate;
  int baseWeight;
  int extraWeight;
  string name;
  base;
public:
  State(string name, double taxRate = 1, int point =0, double baseWeight=2, double extraWeight=1.05); //implement the method yourself
  double extra(double base);
  double basis(double base);
  double calculate(double base){
      return baseWeight * basis(base) + baseWeight * extra(base);
  }
  int point(){return point};

};

Now how to use it:

State ohio ("OHIO", OH_RATE, 2);
cout << "OHIO result:" ohio.calculate() << " point:" << ohio.point() << endl;