It takes 20347.4098071s for light from the sun to reach Pluto. The 6.1*10^9 is replaced by 6.1*10^12 on line 4 because we convert the distance from km to m. c = speed of light. If a different value was given in the previous question then use that instead of the value I used to do the final calculation.
B is located on a positive location, 15m from the starting point A. Hence, since E is located a positive distance 10m from A, the difference becomes 10 - 15 = - 5.0 m