How do I caculate net operating cash flows for years 1, 2, and 3?

Given:

Base price of equipment = $140,000

Cost to modify equipment = $30,000

MARCS 3-year class and would be sold after 3 years for $60,000

Applicable depreciation rates are 33, 45, 15, and 7 percent

Equipment requires an $8,000 increase in working capital (spare parts inventory)

Project has no effect on revenues but should save the firm $50,000 per year before-tax labor costs

Firm's marginal federal=plus tax rate is 40%