$C^{\text{'}}(t)$ and $R^{\text{'}}(t)$ are the following functions.

$C^{\text{'}}(t)=3$

and

$R^{\text{'}}(t)=7e^{-0\mathrm{.}4t}$

Find the area between the graphs of $C^{\text{'}}$ and $R^{\text{'}}$ over the interval on the t $-$axis from $0$ to the useful life of the game and interpret the results.

What is the useful life of the game?

$t=$ years $($Round to the nearest tenth as needed.$)$

The area between the two curve is $$ square units.

$($Round to three decimal places as needed. Use the answer from the previous step to find this answer.$)$