The Table Below Describes the Value Added in the Production

The table below describes the value added in the production of a gallon of gasoline by each stage of production.(The values are hypothetical.)
Table 12-10
$\begin{array}{|l|l|l|}\hline \text { Stage of Production } & \text { Value of Sales } & \text { Value Added } \\\hline \text { Oil drilling } & 0.75 & \\\hline \text { Refining } & 1.25 & \\\hline \text { Shipping } & 1.85 & \\\hline \text { Retail sales } & 3.65 & \\\hline\end{array}$
a)What is the value added by each stage of production?
b)What is the total value added?
For simplicity,you can ignore the cost of the inputs for oil drilling.