Answer:
DV/dt  =  942 cm³/sec  (decreasing )
Step-by-step explanation:
Volume of the sphere   V = 4/3Ï€*r³  Â
r  ⇒ r(t)
DV/ dt   =  DV/dr * Dr/dt    so
DV/dt  = 4*π*r²*Dr/dt
and we know  Dr/dt  = - 3 cm/sec   and r = 5 cm
Then  radius decreasing  V  also decreases
by substitution
DV/dt  = - 4*π*(5)²* (3)
DV/dt  = - 942 cm³/sec