Shipping costs at Columbia Mining Company are a mixture of variable and fixed components. The company shipped 8,000 tons of coal for $400,000 in shipping costs in February and 10,000 tons for $499,000 in March. Assuming that this activity is within the relevant range, expected shipping cost for 11,000 tons would be: a) $548,500 b) $422,222 c) $554,000 d) $544,500