If a = 1001, b = 1002, c = 1003, then the value of a2 + b2 + c2 - ab - bc - ca is

If a = 1001, b = 1002, c = 1003, then the value of a² + b² + c² - ab - bc - ca is

     (a) 2

     (b) 3

     (c) 5

     (d) None of these