The given function is:
[tex]E(t)=3863-77.8t[/tex]This function is written in the form:
[tex]y=b+mx[/tex]Where b is the y-intercept, and m is the slope of the function. In this case, b=3863 and m=-77.8
The slope is negative, it means the function is decreasing, and the rate of decreasing is the value of the slope, so:
The surface elevation of Lake Power is decreasing at a rate of 77.8 ft/year