The investor should take the following steps at time 0:

1. Short sell corn at the spot price of $6.90 per bushel
2. Lend the $6.90 for 1 year at the risk-free rate
3. Take a long position in a 1-year corn forward contract

At the expiration of the futures contract:

1. Receive the lent money with interest for $6.90(1.08) = $7.45
2. Purchase the corn bushel at the forward price of $6.90 and deliver the corn bushel
3. Earn the reverse cash-and-carry arbitrage profit of ($7.45 – $6.90) = $0.55

Note: Selling short comes with a fee, but we ignore that for exam purposes.