If the Surface Area of a Sphere Is Shrinking at the Rate

Multiple Choice

If the surface area of a sphere is shrinking at the rate of 0.1 sq cm/h when the radius is $\frac { 20 } { \pi } \mathrm { cm } \text {, }$ the rate of change of the radius in cm/s is

A) $- \frac { 1 } { 400 }$
B) $- \frac { 1 } { 800 }$
C) $- \frac { 1 } { 1600 }$
D) $- \frac { 1 } { 3200 }$
E) $- \frac { 1 } { 6400 }$