Basis = spot price-futures price. Basis in June = 3300-3 150 = 150, and basis in September =3600-3550=60.
Futures market: I bought 3 150 and sold it at 3,550, so I earned (3,550-3150) * 2,000 tons = 800,000 yuan.
Spot market: I bought it at 3600 instead of 3300, and lost money. Loss (3600-3300)*2000 tons =600000 yuan.
Generally speaking, it is profitable, with profit = 800,000-600,000 = 200,000.