Find the absolute maximum and absolute minimum of the function $f(x,y) = 2x^3 + y^4$ on the region $\lbrace (x,y) \; \vert \; x^2 + y^2 \le 1\rbrace$.

If the absolute max or min occurs at multiple points list them all, separated by commas.

Absolute minimum value:
attained at .

Absolute maximum value:
attained at .