10) At an international competition, 600 young people from 100 different countries participate, and from each country, 6 young people come. The day before the competition, a reception is organized in an enormous hall, which all participants attend. Each one gets to know all the others (except for their fellow countrymen, whom they already know) by shaking their hands. How many handshakes are there?
(A) 89100
(B) 178200
(C) 179700
(D) 356400
(E) 360000
10) The answer is $(\mathbf{B})$. Each of the boys shakes hands with $600-6=594$ other boys. In each handshake, 2 boys are involved, so the number of handshakes is $\frac{600 \times 594}{2}=178200$.