Professor Simpleton has a dilemma. A double dose of artic air is spilling into North Texas, and he needs to keep his garage apartment/office warm for four (4) days by burning wood in his wood stove. He has a limited supply of hickory, red oak, and birch logs to get him through the cold spell. The logs are of a standard size, but each log costs a different amount and puts out a different amount of heat when it is burned (measured in thousands of BTU's).