Final answer:
Exact IRR values for Project T-Shirt and Project Board Shorts cannot be provided without iterations or financial calculators. In practice, the project with IRR higher than the company's cost of capital and fitting its criteria is typically chosen.
Step-by-step explanation:
To compute the internal rate of return (IRR) for each project, we would have to set up an equation that equals the net present value (NPV) of cash inflows to the initial investment, considering each project's lifespan and cash inflows. However, this calculation typically requires the use of financial calculators or software, as it involves solving for the rate that makes the NPV equal to zero. Unfortunately, without concrete data and the ability to use iterations or a financial calculator, I cannot provide the exact IRR values for Project T-Shirt and Project Board Shorts.
As a general guideline, the IRR can be compared against a company's required rate of return or cost of capital. The project with the higher IRR, which exceeds the cost of capital and satisfies other investment criteria set by the company, should be recommended. It is essential to note that the IRR calculation assumes that cash inflows are reinvested at the same rate as the IRR, which may not always be the case in reality.