A sphere of \(30-\mathrm{mm}\) diameter contains an embedded electrical heater. Calculate the power required to maintain the surface temperature at \(89^{\circ} \mathrm{C}\) when the sphere is exposed to a quiescent medium at \(25^{\circ} \mathrm{C}\) for:

(a) air at atmospheric pressure,

(b) water, and

(c) engine oil.