what is the order of 4 × 10^-7, 7 × 10^-9, 1 × 10^4, 2 × 10^4 from least to greatest?

a. 1 × 10^4, 2 × 10^4, 4 × 10^-7, 7 × 10^-9

b. 4 × 10^-7, 7 × 10^-9, 1 × 10^4, 2 × 10^4

c. 7 × 10^-9, 4 × 10^-7, 1 × 10^4, 2 × 10^4

d. 7 × 10^-9, 4 × 10^-7, 2 × 10^4, 2 × 10^4

Expresa commuter train leaves downtown sation and travels at a average speed of 55 miles per hour towards the north side sation, which is 50miles away. thirty minutes later, express commuter train #7 leaves north side and travels at a average speed of 35miles per hour towards downtown sation. at the moment the two trains pass each other, how far(in miles) is train #12 from the downtown sation and how long(in minutes) has the #12 train been traveling