Find the Slope of the Curve at the Indicated Point $80.0 \mathrm {~mm}$

Multiple Choice

Find the slope of the curve at the indicated point.
-A balloon used in surgical procedures is cylindrical in shape. As it expands outward, assume that the length remains a constant $80.0 \mathrm {~mm}$ . Find the rate of change of surface area with respect to radius when the radius is $0.090 \mathrm {~mm}$ . (Answer can be left in terms of $\pi$ ) .

A) $160.36 \pi \mathrm { mm } ^ { 2 } / \mathrm { mm }$
B) $160.0 \pi \mathrm { mm } ^ { 2 } / \mathrm { mm }$
C) $80.36 \pi \mathrm { mm } ^ { 2 } / \mathrm { mm }$
D) $80.18 \pi \mathrm { mm } ^ { 2 } / \mathrm { mm }$