The $\sqrt { \text { str } } = 12 + 20 ($

The $\sqrt { \text { str } } = 12 + 20 ($ dia $)$ can be used to predict the breaking strength of a rope (in pounds) from its diameter (in inches) . According to this model, how much force should a rope onehalf inch in diameter be able to withstand?

A) $16 \mathrm { lbs }$
B) $22 \mathrm { lbs }$
C) $4.7 \mathrm { lbs }$
D) $256 \mathrm { lbs }$
E) $484 \mathrm { lbs }$