Question 1172162
Let's choose P, VP, then S... this is the most straightforward way to go:<br>
(20C1)(30C1)(48C1) = 20*30*48 = {{{ highlight(28800) }}}
The 48 comes from the total 50 - 1 (female for P) - 1 (male for VP) = 48
<br>

But, you say, what if you choose S first?  
Ok, let's do that case.<br>

Choose S first, then P, then VP:

Two independent ways to choose S: (i) female, (ii) male<br>

(i) female S:  (20C1)(19C1)(30C1) = 20*19*30 = 11400<br>
PLUS<br>
(ii) male S:   (30C1)(20C1)(29C1) = 30*20*29 = 17400<br>
                                              
The total # of ways is 11400+17400 = 28800, just as we obtained before.