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. Borrowing cost was 5%, but the lending rate was 4.5% (both compounded semi-annually). 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.