<u><em>Answer:</em></u>
The slope of the line is 77
<u><em>Explanation:</em></u>
We know the speed is constant and that the mile-marker location over time can be represented by a line. This means that the equation is linear.
<u>The slope can, therefore, be calculated as follows:</u>
where (x₁ , y₁) and (x₂ , y₂) are two points on the line
We are given that the two points (1, 123) and (3, 277) are two points in the line
<u>Substitute with them in the above equation to get the slope as follows:</u>
Hope this helps :)