How many of the 60 cars sold last month by a certain dealer had neither power windows nor a stereo?
(1) Of the 60 cars sold, 20 had a stereo but not power windows.
(2) Of the 60 cars sold, 30 had both power windows and a stereo

Here as we know from st.1
20 has no pw no ster. we cant do any thing with that
from St2
30 has both
by adding both info we get number of car having ster.is 20+30=50
as we know
total= a + b - both + neither
60 = 50+ 40 - 30 + Neither
so we can say IMO C

am I missing something?