What is 58,000,000,000 estimated as the product of a single digit and a power of 10?

a. b.

c. d.

Since we are estimating, round to 60,000,000,000. Now count how many decimal places you would have to move to the left to get to a single digit (until we get to 6.0). That will be your exponent ...

6 * 10^10