Mathematics

Problem

The radius of a spherical balloon (in meters) is given by

r(t)=3t-t^{2}

, where

t

is time in seconds for

0<t<3

. At what time

t>0

is the surface area of the balloon neither increasing nor decreasing? a)

t=2.0\text{ s}

t=1.73\text{ s}

t=1.5\text{ s}

t=1.27\text{ s}