Creating derived class from an other namespace - class

Question

I need to do this for one of my subject to get passed.This is the code and my problem is at PDA::class pda_ipari : public pda_basic where i need to create a namespace which has a derived class from an other namespace. Could you help me ?
#include <iostream>
using namespace std;
namespace PDA{
class pda_basic{
private :
float cpu_ghz;
int cpu_core;
int memory;
int storage;
public :
float getGhz()
{
return cpu_ghz;
}
void setGhz(float m)
{
cpu_ghz=m;
}
int getCore()
{
return cpu_core;
}
void setCore(int m)
{
cpu_core=m;
}
int getMemory()
{
return memory;
}
void setMemory(int m)
{
memory=m;
}
int getStorage()
{
return storage;
}
void setStorage(int m)
{
storage=m;
}
};
}
namespace abtu9p_pda{
PDA::class pda_ipari : public pda_basic {
private:
float display;
string vonalkodTipus;
int ip_vedelem;
public:
float getDisplay()
{
return display;
}
void setDisplay(float m)
{
display=m;
}
string getVonalkod()
{
return vonalkodTipus;
}
void setVonalkod(string m)
{
vonalkodTipus=m;
}
int getIP()
{
return ip_vedelem;
}
void setIP(int m)
{
ip_vedelem=m;
}
};
}
int main()
{
PDA::pda_basic tablet;
tablet.setGhz(2.7);
cout <<tablet.getGhz()<<endl;
return 0;
}