The north american numbering plan (nanp) is a telephone numbering plan that encompasses 25 distinct regions in twenty countries primarily in north america, including the caribbean and the u. s. territories. the nanp divides the territories of its members into numbering plan areas (npas) which are encoded numerically with a three-digit telephone number prefix, commonly called the area code. (a) it’s regulated that the first digit cannot be 0 or 1. then how many possible area code are there? (b) what is the probability that an area code assigned at random has at least one 0?