Suppose that x is the yield on a perpetual government bond that pays interest at the rate of $ 1 per annum. Assume that x is expressed with continuous compounding, that interest is paid continuously on the bond, and that x follows the process dx = a(x0 —x)dt + sx dz where

a, x$, and s are positive constants and dz is a Wiener process. What is the process followed by the bond price? What is the expected instantaneous return (including interest and capital gains) to the holder of the bond?