The 1-week call options on the Alibaba stock with strike prices of $185, $190, and $195 are $10, $7, and $5.5, respectively. An investor longs a butterfly spread using these three options. Specifically, he longs 100 call options with the strike price $185, shorts 200 call options with the strike price $190, and longs 100 call options with the strike price 195. What is the investor's maximum gain from this strategy?