Create a stepwise approach to estimate how much dietary protein must be consumed daily to achieve a positive protein balance of +10 g/day if endogenous recycling supplies 210 g/day but has an unavoidable 15% loss to oxidation/excretion. No digestion inefficiencies for dietary protein are assumed; show the algebraic setup and numeric result.

• A. Approximately 210 g/day since you must replace the entire recycled supply with diet to achieve any net positive balance.
• B. Approximately 178.5 g/day because diet is irrelevant when recycling provides the entire pool and you only need to match exactly the recycled amount to achieve any positive balance.
• C. Approximately 10 g/day dietary protein is required under the stated assumptions because net recycled supply (210 g × 0.85 = 178.5 g) is assumed to meet maintenance and an additional 10 g is needed for net positive balance.
• D. Approximately 40 g/day because you must multiply the net recycled amount by the desired positive balance percentage, yielding roughly 210×0.15 ≈ 31.5 and rounding upward to 40 g/day to be safe.

Answer: (C)