Would each of the following increase, decrease, or have an indeterminant effect on a firm's break-even point (Unit Sales)?

a. The sales price increases with no change in unit costs.

b. An increase in fixed costs is accompanied by a decrease in variables costs.

c. A new firm decides to use MACRs depreciation for both book and tax purposes rather than the straight-line depreciation method.

d. Variable labor cots decline, other things are held constant.