projected cash flows

Sandoval Enterprises has gathered the projected cash flows for two projects. At what interest rate would the firm be indifferent between the two projects? Which project is better if the WACC is above the interest rate? Why?
Year Cash Flow I Cash Flow J0 -$38,000 -$38,0001 20,000 15,0002 18,000 17,0003 16,000 19,0004 14,000 21,000