Problem:A publishing house has found that in a certain city each of its salespeople will sell approximately, 
> ;
2 r 2 1/2000  + 1/100 s  s p
units per month, at a price of p dollars/unit, where s denotes the total
number of salespeople employed and r is the amount of money spent each month
on local advertising. Express the total revenue R as a function of p,r and s.

> ;
/ 2 \  r 2  R = 1/2000  + 1/100 s  s p s  r \ p /