By mixing available fuel, you need to produce 3500 gallons of gasoline for your feet of trucks

Question:

By mixing available fuel, you need to produce 3500 gallons of gasoline for your feet of trucks this month. You plan to mix 800 gallons of fuel A (80 octane), 1500 gallons of fuel B (92 octane) and 1200 gallons of fuel C (78 octane). Use the weighted average approach to compute the octane rating for the resulting mix.