Provide your best answer for the following math problem. Give ONLY the answer, no other words or explanation.
For example:

Answer: <most likely answer, as short as possible; not a complete sentence, just the answer!>.

The problem is: spheres a and b have their radil 40 cm and 10 cm respectively . the ratio of the surface area of a to the surface area of b is
16 : 1'
16:1.