Hint$($s$)$:

$1)$ For a$)\backslash$& b$)200$ and $1200$ stadent's.

$2)$ For c$)1)$ The profit c$)2)$ The dectacke

will be greater than ifook

while The increase

c$)3)$ The increase will axceed $30$k

While the decrease will exceed Ho K K