An office is buying printers for their headquarters, a premium model and regular model. The premium model can print 30 pages per minute while the regular model can print 20 pages per minute. In addition, the premium model requires 4 units of ink per minute while the regular model requires 3 units of ink per minute. The office wants to make sure that at least 200 pages can be printed per minute and that at most 35 units of ink are used per minute.  Since the premium model is more user friendly, the number regular printers must be less than the number of premium printers. How many of each printer should be bought to minimize the total number of printers in the office?