Choice (A) was a trap for Joe: when he doesn't know what to do on tough questions, Joe gets in a panic and chooses numbers straight out of the problem.
Actually, this is the correct answer to the problem. For the Joe Bloggs answers, try again.
This is the classic Joe Bloggs answer: all he has to do is add the two numbers in the problem. This is one of the most difficult problems in its section (#23 out of 25 problems.) 30% is too easy to be the answer to such a difficult problem.
