Thirty days of one carry trade, on capital

In a cash-and-carry trade, what makes the coin's price moves cancel out?

• Equal dollar values in the two legs
• Equal coin counts in the two legs
• Holding the short on isolated margin

Why is return on capital lower than return on notional for the same carry trade?

• Because fees are counted only on capital
• Because capital includes the short's margin as well as the spot cost
• Because notional ignores funding