With the Resources Available, You Can Make the Combinations of Ums

With the resources available, you can make the combinations of Ums and Umies (trinkets from a place called Bandarban) shown in the table. The opportunity cost of producing 60 Umies instead of 30 Umies is: $\begin{array}{|c|c|}\hline \text { Number of Ums } & \text { Number of Umies } \\\hline 60 & 0 \\\hline 40 & 30 \\\hline 20 & 60 \\\hline 0 & 90 \\\hline\end{array}$

A) 10 Ums
B) 20 Ums
C) 30 Ums
D) 40 Ums