Download the Credit Card Library from Lucas Carlson.

sudo gem install creditcard
# Checksum Digit, there is an algorithm that checksum must match

# A. Import the libraries
require 'rubygems'
require 'creditcard'

# B. Boolean test as to whether this number is a valid credit card
puts '5276 4400 6542 1319'.creditcard?

# C. Check the type of credit card it is
puts '5276 4400 6542 1319'.creditcard_type