Stephen evaluated (6.34 times 10 Superscript negative 7 Baseline) (4.5 times 10 Superscript 3 Baseline). His work is shown below. Which two statements describe the errors Stephen made?

(6.34 times 10 Superscript negative 7 Baseline) (4.5 times 10 Superscript 3 Baseline). (6.34 times 4.5) (10 Superscript negative 7 Baseline times 10 Superscript 3 Baseline). 28.53 times 10 Superscript negative 4 Baseline. Negative 28.53 times 10 Superscript 4 Baseline. Negative 2.853 times 10 Superscript 3 Baseline.

He changed the sign of the coefficient in Step 4. A negative exponent does not affect the sign of a coefficient in scientific notation. The sign of the exponent determines the direction the decimal is moved in.
He rewrote Negative 28.53 times 10 Superscript 4 incorrectly in Step 4. The coefficient will need to be rewritten in scientific notation that is less than 1 or greater than 10.

He did not correctly evaluate the exponent. It should be evaluated as (10 Superscript negative 7 Baseline times 10 Superscript 3 Baseline) = 10 Superscript negative 21 since exponents are evaluated using the same operation as the coefficients.
He multiplied the coefficients; he should have subtracted 6.34 and 4.5. Resulting in a new coefficient of 1.84.
He multiplied the coefficients; he should have added 6.34 and 4.5. The product of powers rule states that coefficients are added.