Consider the reaction

$2H_{3}P{O}_4{P}_2{O}_5+3H_{2}O$

Using the information in the following table, calculate the average rate of formation of $P_2{O}_5$ between $10\mathrm{.}0$ and $40\mathrm{.}0s.$

$\backslash$table$[[$Time $(s),0,10\mathrm{.}0,20\mathrm{.}0,30\mathrm{.}0,40\mathrm{.}0,50\mathrm{.}0],[[P_2{O}_5](M),0,2\mathrm{.}70{10}^{-3},5\mathrm{.}70{10}^{-3},7\mathrm{.}50{10}^{-3},8\mathrm{.}70{10}^{-3},9\mathrm{.}30{10}^{-3}$