Completey stuck on this one, anyone able to help please!?

A drop of oil (volume 0.05cm3) Is released from a medicine dropper on a calm surface of a pond where it spreads out to cover an area of 40cm2. Assume that the oil film has a uniform thickness equal to the diameter of an oil molecule. Calculate the diameter of an oil molecule and express your answers in scientific notation to an appropriate number of significant figures.