Validating phone number in ruby

Question

What are the rules for validating a North American phone number? Also, is there a regex I can use? Is there a gem to do this?

Here are few rules I have

Answer 1

class Phne
def ad
puts "Enter your phone number"
re=gets.chomp
if re= ~/\b^([0-9]{10})$\b/
puts "Valid phone number"
else
puts "Invalid phone number"
end
end
end

obj=Phne.new
obj.ad