Describe a strategy for Abritrage profit and compute profit [financial mathematics]

Jul 2015
United States
Not sure how to go about this...I know the correct price (fair price) would be k=(S)(e^rt) where S is the original price of stock bought for and e^rt is compound interest formula... arbitrage profit means that NO RISK is involved. So we cannot just assume that it will go up. How about this:
Regardless if I lose profit, make profit, or break even, would a strategy be to after the 3 months, create another contract with someone else on the share I bought, which I would sell for at 31.... in x amount of months...I would say no.