Answer
(a) $70^{\circ} F, 76^{\circ} F, 85^{\circ} F$
and
(b) $75^{\circ} F$
Work Step by Step
(a) Consider: $T(t)=85-3\sqrt {25-t}$
Now,
$T(0)=85-15=70^{\circ} F; \\ T(16)=85-9=76^{\circ} F; \\ T(25)=85^{\circ} F$
b) Let us consider the integral $T=\dfrac{1}{25}\int_{0}^{25} 85 - 3\sqrt {25-t} dt=\dfrac{1}{25} (85(25)+0-0-(2)(125)]=75^{\circ} F$
or,
$T=\dfrac{1}{25} (85(25)+0-0-(2)(125)]=75^{\circ} F$
