Assuming a constant mix of $4$ units of Zip for every $5$ units of Zap, a per$-$unit selling price of $$25\mathrm{.}00$ for Zip and $$40\mathrm{.}00$ for Zap, variable costs per unit of $$16\mathrm{.}00$ for Zip and $$22\mathrm{.}00$ for Zap, and total fixed costs of $$189,000,$ the breakeven point in units would be $\_\_\_\_\_.$

A$)4,000$ units of Zip and $5,000$ units of Zap

B$)6,000$ units of Zip and $7,500$ units of Zap

C$)10,000$ units of Zip and $5,000$ units of Zap

D$)54,000$ units of Zip and $67,500$ units of Zap