Answer:
The total sales of 2003 it's $24.331
Step-by-step explanation:
The Midpoint Formula let us to find the exact center point between two values, always assuming that the sale followed a linear pattern, with this formula it's possible to determinate the value a the center point, in this case year 2003.
Please see details bellow:
1999 : $19.805
2003= $19.805 + ($28.857-$19.805)/2 = $24.331
2007: $28.857