8%的投资回报所要求得销售额用以下的公式来计算
8%的投资回报= [(边际贡献率)(销售额)– 固定成本](1 – 税率)
投资= $300,000，8%的回报= (0.08)($300,000) = $24,000
边际贡献率= (1 – 变动成本率) = (1 – 0.3) = 0.7。因此，设S=销售额
$24,000 = [(0.7)(S) - $600,000](1 – 0.4)
$24,000 = [0.7S - $600,000](0.6)
$24,000 = (0.42S - $360,000)
$384,000 = 0.42S
S = $914,285.71，大约是$914,286
