The diagram represents the factorization of a2+8a+12. A 2-column table with 2 rows. First column is labeled a with entries a squared, 2 a. Second column is question mark with entries 6 a, 12. First row is labeled a with entries a squared, 6 a. Second row is labeled 2 with entries 2 a, 12.

What is the missing number that will complete the factorization?

6
8
12
24