You've invested $10,000 in a portable bratwurst stand, giving up the 8% rate of return you could have earned had you invested that money elsewhere. Last year you sold 1600 brats at $3 each; the meat, buns, and condiments cost you $400.
If you'd spent your time working at your brother's ice cream shop instead of at your brat stand, he'd have paid you $3200. Your economic profit last year was ?