scientific notation

Scientific Notation
1. Which shows the expression below simplified?

(8.9 × 10-4) - (3.8 × 10-5)

a.)8.52 × 10-5
b.)5.1 × 10-4
c.)8.52 × 10-4
d.)5.1 × 10-5
the part where it saus 10-5 and 10-4 are 10 to the negative 4th power and 10 to the 5th power