Question 1103433
a.  This is 10 C 5 =252 ways
b. 3C2*7C3, since there have to be 3 physicists.  This is 3*35=105
c. At most 3 physicists includes the first of 105
2 physicists and 3 chemists, which is 3C3*7C2=1*21=21 ways
1 physicist and 4 chemists doesn't work, because there are only 3 chemists.
therefore, 126 ways. ANSWER