I've been splitting up the funds between three strike prices. Mostly the $12.50 and $15.00 calls, but I picked up some $10.00 calls as well. I have found it's best to spread out when buying options because the prices can fluctuate counterintuitively sometimes. As long as the market doesn't turn sour, I don't see why these commons can't hit at least $20 when it's time to vote for the merger to complete. That would be roughly 80% and 100% return on these calls. This is not investing advice by the way. If the market crashes, you can lose big time with options. So manage your portfolio wisely and be prepared for volatility if you're not familiar with them.
Here's a good resource for approximating returns on options: optionsprofitcalculator.com/
Here's the percentage value approximation chart for the July $12.50 call option if you paid $4.40 for one today and the commons reach $20 in the first week of April: