Which of the following correctly adds numbers in scientific notation: (2.3×104)+(7×103)(2.3 \times 10^4) + (7 \times 10^3)(2.3×104)+(7×103)?
9.3×1049.3 \times 10^49.3×104
2.3×1072.3 \times 10^72.3×107
3×1043 \times 10^43×104
2.3×1032.3 \times 10^32.3×103