Contribution margin is calculated via subtracting the variable cost per unit to the sales price per unit. In equation, we have
Contribution margin = Sales Price - Variable Cost
Contribution margin ratio is calculated via dividing the contribution margin with the sales price. In equation, we have
Contribution margin ratio = contribution margin/sales price
Substituting the given values,
Contribution margin ratio for 65$ variable cost = (120-65)/120 = 0.4583
Contribution margin ratio for 58$ variable cost = (120-58)/120 = 0.5167
ANSWERS: 0.4583 or 45.83% and 0.5167 or 51.67%