Davison Co$.$ prepared the following contribution format income statement based on a sales volume of $10,000$ units $($the relevant range of production is $5,000$ units to $15,000$ units$)$:

Sales $ $210,000$

Variable expenses $126,000$

Contribution margin $84,000$

Fixed expenses $63,000$

Net operating income $ $21,000$

Required:

What is the variable expense ratio?