Data Sufficiency

Q33:
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 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.
Ans :a

Please explain