A restaurant group tracks contribution margin by offering: Lunch: baseline $6 and 15,000 units; current $6.50 and 14,000 units; Dinner: baseline $14 and 8,000 units; current $15 and 8,500 units; Private event: baseline $90 and 500 units; current $94 and 700 units. For contribution margin, use contribution dollars per unit in the same PVM bridge: volume at baseline mix and margin, mix at baseline margin, and rate effect at current units. What is the contribution-margin rate effect, analogous to the price effect?