Fred's Fabrication, Inc. wants to increase capacity by adding a new machine. The firm is considering proposals from vendor A and vendor $B.$ The fixed costs for machine A are $$90,000$ and for machine $B,$$$70,000.$ The variable cost for $A$ is $$9\mathrm{.}00$ per unit and for $B,$$$14\mathrm{.}00.$ The revenue generated by the units processed on these machines is $$20$ per unit. The crossover between machine A and machine $B$ is

$4,000$ dollars, with A more profitable at low volumes.

$4,000$ dollars, with B more profitable at low volumes.

$4,000$ units, with B more profitable at low volumes.

$8,000$ units, with B more profitable at low volumes.

$4,000$ units, with A more profitable at low volumes.