What was not a key lesson of the Empirical Chemicals case study

a$.$ We should not always trust the numbers in capital budgeting proposals. They are often assumptions made by people who want to project to be accepted, for their own personal benefit.

b$.$ When a company adds more debt to its capital structure $($leverage$),$ it's equity $($the shares of common stock$)$ becomes more risky, demanding a higher return. But because the cost of debt tends to lower than the cost of equity, the WACC may well stay unaffected by a change in "leverage"

c$.$ Some projects come with valuable flexibility. "Real" options to $($expand$,$ switch, or abandon$)$ have value and should be taken into account, even though they are difficult to value

d$.$ In capital budgeting, we should take into account all incremental cashflows to the firm, also the cashflows that affect other divisions. We should however not take into account that are not incremental, such as sunk costs or overhead allocations.