credit card number validation) Credit card numbers follow certain patterns. USES CLASSES AND OBJECTS
	* 1. Double every second digit from right to left. If doubling of a digit results in a
	* two-digit number, add up the two digits to get a single-digit number.
	*
	* 2. Now add all single-digit numbers from Step 1.
	* 4 + 4 + 8 + 2 + 3 + 1 + 7 + 8 = 37
	*
	* 3. Add all digits in the odd places from right to left in the card number.
	* 6 + 6 + 0 + 8 + 0 + 7 + 8 + 3 = 38
	*
	* 4. Sum the results from Step 2 and Step 3.
	* 37 + 38 = 75
	*
	* 5. If the result from Step 4 is divisible by 10, the card number is valid; otherwise,
	* it is invalid. For example, the number 4388576018402626 is invalid, but the
	* number 4388576018410707 is valid.