NORTHWIND: The Order Details Discount field contains fractional values such as $0\mathrm{.}02,0\mathrm{.}05$ but also zeros and these values represent a percentage discount off of the total order amount. E$.$g$.,0\mathrm{.}02$ represents a $2\%$ discount. List all of the products sold in May $2015$ and for each sale the total value of the discount. Total value is the money NorthWind did not collect because of the discount compared to what full price revenue would have been. $($SQL$)$