A cylinderical oil tube, lying horizontally, has an interior length of 10 cm and aninterior radius 3 cm. If the rectangular surface of the oil has an area of 40 cm?, the depth ofoil in the tube is

A

$$\sqrt{5}$$ cm

B

$$2\sqrt{5}$$ cm

C

$$(\sqrt{5} - 2)$$ cm or $$(\sqrt{5} + 2)$$ cm

D

either $$(3 - \sqrt{5})$$ cm or $$(3 + \sqrt{5})$$ cm