1. The problem asks to round the total energy supplied, which is 873600 J, to 2 significant figures. 2. Identify the first two significant figures in 873600: they are 8 and 7. 3. Look at the digit after the second significant figure to decide whether to round up or down. The third digit is 3. 4. Since 3 is less than 5, we round down. 5. Therefore, rounding 873600 to 2 significant figures gives 870000. 6. In scientific notation, this is written as $$8.7 \times 10^{5}$$ J. Final answer: 870000 J (rounded to 2 significant figures).