问一道题~！红色OG第284页第124题~~求解释~~

selinsia

	favorable	Unfavorable	Not sure
Candidate M	40	20	40
Candidate N	30	35	35

The table above shows the results of a survey of 100 voters who each responded "Favorable" or "unfavorable" or "not sure" when asked about their impressions of candidate M and of candidate N. What was the number of voters who responded "favorable" for both candidates?

(1)The number of voters who did not respond "Favorable" for either candidate was 40.

(2)The number of voters who responded "unfavorable" for both candidates was 10.


为什么第二个选项也是对的呀？解释没看懂~~求帮助~~~！！！万分感谢呀~~