Compute (6.0×104)+(4.0×103)(6.0 \times 10^4) + (4.0 \times 10^3)(6.0×104)+(4.0×103) in scientific notation.
1.0×1081.0 \times 10^81.0×108
6.4×1046.4 \times 10^46.4×104
10×10410 \times 10^410×104
6.4×1036.4 \times 10^36.4×103