The Flamey-Wamey Company (FWC) produces extinguishers and heat detectors. Each extinguisher takes three hours of labor from the materials department and four hours of labor from the contruction department. Each heat detector requires three hours of materials and two hours of construction. During the current week, 120 hours of materials time are available and 150 hours of construction time. Each extinguisher produced gives a profit of £12 and each heat detector a profit of £10. How many heat detectors and extinguishers should be made?