STU Plc is evaluating two potential projects, Project X and Project Y, both requiring an initial investment of USD 600,000. The expected cash flows and profits for each project are as follows:

Project X:

• Year 1: Cash Flow - $100,000, Profit - $10,000
• Year 2: Cash Flow - $150,000, Profit - $20,000
• Year 3: Cash Flow - $200,000, Profit - $30,000
• Year 4: Cash Flow - $250,000, Profit - $40,000
• Year 5: Cash Flow - $300,000, Profit - $50,000

Project Y:

• Year 1: Cash Flow - $120,000, Profit - $15,000
• Year 2: Cash Flow - $170,000, Profit - $25,000
• Year 3: Cash Flow - $220,000, Profit - $35,000
• Year 4: Cash Flow - $270,000, Profit - $45,000
• Year 5: Cash Flow - $320,000, Profit - $55,000
• Cost of Capital: 12%

Tasks: a) Explain the relevant costs in investment decisions. b) Contrast between payback period and internal rate of return (IRR). c) Calculate for both projects: i) The payback period. ii) The net present value (NPV). iii) Recommend which project STU Plc should undertake, with justification.