a$.$ Equipment costing $$6,000$ with accumulated depreciation of $$2,000$ sold for $$5,700$ cash.

b$.$ Gain on the sale in $"$a$"$ is $$1,700.$

The operating section would include a subtract of $$1,700$ to back out the gain; and the investing section would include an inflow of $$5,700.$

The operating section would include an add of $$1,700$ to back out the gain; and the investing section would include an inflow of $$6,000.$

The operating section would include a subtrapt of $$1,700$ to back out the gain; and the financing section would include an inflow of $$5,700.$

The operating section would include a subtract of $$1,700$ to back out the gain; and the investing section would include an inflow of $$2,000.$