11. Add the numbers 5.1 x 10^5 and 3.0 x 10^3

a. 3.051 x 10^3
b. 3,051 x 10^5
c. 30,.51 x 10^3
d. 305.1 x 10^5

12. Multiply 5.1 x 10^5 by 3,0 x 10^3

a.1.53 x 10^6
b. 1.53 x 10^7
c. 1.53 x 10^8
d. 1.53 x 10^9​