Alibaba is currently trading at 114.97 a share and you don’t expect its price to move much in the next 31 days. Alibaba’s 115 at-the-money calls are quoted as follows:
Bid Ask Bid Ask
115 8-day 1.51 1.60 115 24-day 3.40 3.50
115 17-day 1.98 2.07 115 31-day 3.65 3.80
Is there a reasonably safe arbitrage opportunity for profit here? Please explain your strategy and compute the gain or loss if, in 8 days, Alibaba (1) increases to 120, (2) remains unchanged, or (3) drops significantly.