please solve this, functional programming.

$10.\backslash (\backslash$square $\backslash )$ mystery$-$func returns the value $\backslash ((-$x $1)\backslash )$ when it reaches the base case.

$11.\backslash (\backslash$square $\backslash )$ The depth of recursion in mystery$-$func depends on the size of the argument $\backslash ($ y $\backslash ).$

$12.\backslash (\backslash$square $\backslash )$ The mystery$-$func function accumulates the sum of the numbers from y to $1.$

$13.\backslash (\backslash$square $\backslash )$ mystery$-$func cannot handle negative values of $\backslash ($ x $\backslash ).$

$14.\backslash (\backslash$square $\backslash )$ Testing mystery$-$func, with arguments $\backslash ((5,0)\backslash )$ returns $15.$

$15.\backslash (\backslash$square $\backslash )$ Testing mystery$-$func with arguments $\backslash ((5,0)\backslash )$ returns $14.$

$16.\backslash (\backslash$square $\backslash )$ Testing mystery$-$func with arguments $\backslash ((5,0)\backslash )$ returns $16.$