How to calculate Bill by predefine Value Java Program

class bill
{
public static void main (String arg[])
{
double pr,cr,un,ba;

/*pr = previous reading , cr= current reading, un= consume units, ba= bill amount*/
pr=700;

cr=1500;
un= cr-pr;

ba= 5*un; /* 5 is rate per unit*/

System.out.println ("Your Consume Units is : "+un);

System.out.println ("Your bill amount is : "+ba);


System.out.print("\n\n\t\tDeveloped by AhsAn....!!\n\n\n");

}

}