$12.$you want to build a $1100$ square foot rectangular infinity pool. Three of the sides will have regular pool$$ walls, and the fourth side will have the infinity pool wall. Regular pool walls cost $$$$14$ per foot$($regardless of how deep the pool$$ is$),$ and the infinity pool wall costs $$$$35$ per foot$($regardless of$$ depth$).$ What is the least that your pool can$$ cost$?$

It will cost $$$

$13.$You want to build a $1200$ square foot rectangular infinity pool. Three of the sides will have regular pool$$ walls, and the fourth side will have the infinity pool wall. Regular pool walls cost $$$$16$ per foot$($regardless of how deep the pool$$ is$),$ and the infinity pool wall costs $$$

$25$ per foot$($regardless of$$ depth$).$ How long should you make the infinity wall so that you minimize your$$ costs?

It should be $\_\_\_\_$ feet