4. In space, there are 2004 points, no three of which are collinear. Divide them into 30 groups with different numbers of points. From any 3 different groups, take 1 point from each to form a triangle. To maximize the total number of such triangles, how many points should be in each group?
(Let the number of points in each group be $x_{1}, x_{2}, \cdots, x_{30}$, and $x_{1}<x_{2}<\cdots<x_{30}$. First, prove $1 \leqslant x_{t+1}-x_{i} \leqslant 2$. Then, prove that between 1 to 30, there is at most one $i$ such that $x_{t+1}-x_{t}=2$. Finally, find $52,53, \cdots, 72,74, \cdots, 82$.)