A fire department employs regular and emergency fire fighters. A regular fire fighter works 10 hours per shift and earns $300. An emergency fire fighter works 6 hours per shift and earns $100. Due to wildfires in the region, the fire department needs at least 300 hours of fire fighter time. If the fire department has a budget of $7000, how many of each should the fire department hire to minimize the total number of fire fighters?