Restrictions on short selling mean that a reverse cash-and-carry trader (one who is long the futures contract and simultaneously short the underlying asset) can only receive the use of 85% of the proceeds of oil sold short. Other than this restriction the market is free from transaction costs, arbitrage opportunities, and taxes. What is then the permissible range of oil futures prices, if spot oil is trading at $50, the risk-free rate is 5% (compounded semi-annually), and expiration is six months away?

Please explain in Excel showing formulas for replication.