A finned tube is to be used for a heat transfer operation that involves engine oil. The tube and fins are made of copper with the fins being \(4 \mathrm{~cm}\) on a side and \(1 \mathrm{~mm}\) thick. The oil flows over them at a velocity of \(1 \mathrm{~m} / \mathrm{s}\) and is at a nominal temperature of \(300 \mathrm{~K}\). The tube and fins are at a uniform temperature of \(360 \mathrm{~K}\). Determine the minimum fin spacing for this scenario that allows us to use the maximum number of fins per unit length of tube.