How to calculate capital gain taxes ? (long term and short term)

We'll have $100K income in 2013, and $50K is our salary and $50K are capital gains ($20K is short term capital gain and $30K is long term). Since the tax rate changes at $72,500, what is the best way to estimate our taxes? Should we do salary + ST capital gain first, then add the LT on top? Or vice versa (salary + LT gain, then add ST gain)? Thanks in advance for your reply.