GWD数学题

melody远行

Last year in a group of 30 businesses, 21 reported a net profit and
15 had investments in foreign markets. How many of the businesses
did not report a net profit nor invest in foreign markets last year?
(1) last year 12 of the 30 businesses
reported a net profit and had invest-
ments in foreign markets.
(2) last year 24 of the 30 businesses
reported a net profit or invested in
foreign markets, or both.

这题给的答案是B，可是我觉着第一个条件单独也是可以求出答案的。第一个条件说的是同时有二者的人数是12吧？