You're at a Starbucks coffee shop in Chicago on a cold winter day. You get a large cup of hot coffee and small cup of room temperature liquid creamer on the side. You will then leave the Starbucks shop and cross the street (in the minus zero degree weather) to get to your office building, sit down at your desk and take your first sip of the coffee. If you want to maximize the temperature of the coffee by the time you sit down at your desk, do you add the creamer before you leave the coffee shop or after (when you're at your office desk)?