Answer:
C 6.45x 10 to the power of 10
Explanation:
10 to the power of 5 is 100,000. 7.5x100,000 is 750,000.
10 to the power of 4 is 10,000.
10,000x8.6 is 86k
now we do 750,000x86,000 which is 64,500,000,000
10 to the power of 10 is 10 billion times 6.45 is 64,500,000,000