Each answer starts with the setup, shows the steps, and closes with the interview takeaway.
Separate the two WACC effects
Which has a bigger effect on valuation: a 1% change in the perpetuity growth rate or a 1% change in WACC?
Both move the terminal-value denominator by one percentage point. WACC also changes every discount factor.
Terminal valueIn the Gordon growth formula, TV = FCF × (1 + g) / (WACC - g). A 1% move in either WACC or g changes the denominator by the same absolute amount.
DiscountingWACC also discounts each forecast cash flow and the terminal value back to today. The growth rate does not change those discount factors.
ConclusionThe 1% WACC change has the larger total valuation effect, holding the rest of the setup constant.
Interview check: mention both the terminal-value denominator and present-value discounting.
Walk $10 of depreciation
$10 of depreciation with a 40% tax rate - walk through the three statements.
Depreciation lowers earnings but is non-cash, creating a tax shield.
Income statementEBIT -$10; taxes -$4NI -$6
Cash flow statementNI -$6 + D&A $10Cash +$4
Balance sheetCash +$4; PP&E -$10Assets -$6
Balance: retained earnings falls by $6, matching the $6 net decline in assets.
Clarify the cash-flow timing
$45 of free cash flow with a 12.5% discount rate - how much would you pay for it?
The answer changes completely depending on whether $45 is a one-time cash flow or a perpetuity.
Perpetuity$45 / 12.5%$360 present value
One year only$45 / 1.125$40 present value
Best response: ask whether the cash flow repeats, grows, and when it is received before calculating.