Explanation

We read the question and don't find exactly what we expected at the end of the question, because we thought that the question was going to ask us the height of the stack. Rather than simply reread it, we'll scan it backwards. Statement (2) implies that we don't necessarily know the height of the stack. Statement (1) tells us about b. At the end of the question, it's asking us to compare a and b. What are a and b? The numbers of each type of block. And we know a lot, actually, because we know there are 12 blocks total and we know their heights. Very well; let's turn to the statements, separately first.

Statement (1) tells us that b is greater than 5. We can construct cases. Case I: . Is this case allowed? Yes, because b is greater than 5 and the total number of blocks is 12. Case II: , and again the two total 12. In both cases, the answer to, Is ?, is "no." And b only goes up in the other possible cases, with a going down. Hence we have sufficient information to answer the question. Statement (1) is sufficient.

Statement (2) tells us that . We know, meanwhile, that . The latter equation is the same as , and we can subtract that from the inequality to get . Smooth, right? It's the same as subtracting 48 from both sides, since 48 is equal to . Then we can examine cases. Case I: . Case II: . In one case, the answer to is "no," and in the other, it's "yes." We don't have sufficient information to answer the question definitively, so Statement (2) is insufficient.

The correct answer is (A).