Answer:
a)
[tex](4.3 \times {10}^{5} )(1.6 \times {10}^{4} ) = 6.88 \times {10}^{9} [/tex]
b)
[tex](2.25 \times {10}^{3} )(5.8 \times {10}^{6} ) = 13.05 \times {10}^{9} = 1.305 \times {10}^{10} [/tex]
I hope I helped you ^_^