A college print shop leases an industrial Xerox photo copier for $$1,500$ per month plus $1\mathrm{.}5$ for every page. Additional

printing costs are estimated at $2$ per page, which covers toner, paper, labour, and all other incurred costs. If copies are

made for students at $10$ each, determine the following:

a$.$ How does net income change with every $100$ copies sold?

b$.$ What is the monthly net income if$,$ on average, the shop makes $25,000$ copies for students each month?