/// <summary>
/// Process the product of the count of product numbers that contains a letter 3 times and the count of product numbers that contains
/// a letter 2 times.
/// </summary>
/// <returns>The product of the two counts.</returns>
/// <param name="numbers">The list of product numbers.</param>
public int Part1(string[] numbers)
{
int two = 0;
int three = 0;
foreach (string number in numbers)
{
PartNumber.Checks check = PartNumber.Checksum(number);
if (PartNumber.HasLetterTwice(check))
{
two++;
}
if (PartNumber.HasLetterThreeTimes(check))
{
three++;
}
}
return(two * three);
}