In an effort to reduce the mass of an aluminum bulkhead for a spacecraft, a machinist drills an array of holes in the bulkhead. The bulkhead is a triangular-shaped plate with a base and height of 2.5 m and 1.6 m, respectively, and a thickness of 8 mm. How many 5 cm diameter holes (no partial holes) must be drilled clear through the bulkhead to reduce its mass by 8 kg? The density of aluminum is ρ = 2800 kg/m3.