Look at the following class definition, which statements are legal and which are illegal. Explain why

class Vehicals{

private:

int sedan;

int trucks;

int planes;

int boats;

publics:

Change() { sedans= trucks= planes= boats= 0; }

Change(int s, int t, int p, int b) { sedans= s ; trucks= t; planes= p; boats= b; }

void add(int s=0, int t=0, int p=0, int b=0)

{ sedans+= s; trucks += t; planes += p; boats+= b; }

void subtract(int s=0, int t=0, int b=0, int p=0)

{ sedans-= s; trucks -= t; planes -= p; boats-= b; }

}