polymorphism on abstract class

Question

hello... i have an issue and need help... i will calculate two circuits with two resistors, parallel or serie... for this i have created an abstract class KretsDel, which has two protected fields(resistors), and abstract property, Total and a constructor.

 

further i have created two classes Parallel and Serie, which contains the propertyTotal which returns the result of resistors connections.

 

further i have created a class Krets with a field List<KretsDel> and two methoder for calculation of serie or parallel coupling for each element in List<KretsDel>... but i get errors...

 

the following is my codes:

class Program
{
static void Main(string[] args)
{
Krets k = new Krets();
}
}
abstract class KretsDel
{
protected float R1, R2;
public abstract float Total
{
get;
set;
}
public KretsDel(int r1,int r2)
{
this.R1 = r1;
this.R2 = r2;
}
}
class Parallel : KretsDel
{
override public float Total
{
set
{
this.R1 = value;
this.R2 = value;
}
get { return parallel(this.R1, this.R2); }
}
public float parallel(float r1, float r2)
{
float R = r1 *r2 / (r1 + r2);
return R;
}
}
class Serie : KretsDel
{
override public float Total
{
set
{
this.R1 = value;
this.R2 = value;
}
get { return serie(this.R1, this.R2); }
}
public float serie(float r1, float r2)
{
float R =r1 + r2;
return R;
}
}
public class Krets
{
static Parallel parallel = new Parallel();
static Serie serie = new Serie();
List<KretsDel> lkd = new List<KretsDel>() { parallel, serie };
foreach(var k in lkd)
k.Total;
public float ser(float r1, float r2)
{
float R = r1 + r2;
return R;
}
public float para(float r1, float r2)
{
float R = r1 * r2 / (r1 + r2);
return R;
}
}

appreciate any help... kind regards