Lake sales had $2,500,000 in sales last month
the contribution margin ratio was 35% = 35/100 = 0.35
operating profits were $175,000
Fixed costs = $2,500,000 × 0.35 - 175,000
=$875,000 - $175,000
= $700,000
$700,000/.35 = $2,000,000
Margin of safety = $2,500,000 - $2,000,000 = $500,000