Suppose that $x$ is the yield to maturity with continuous compounding on a zero-coupon bond that pays off $$\$ 1$$ at time $T$. Assume that $x$ follows the process
$$
d x=a\left(x_0-x\right) d t+s x d z
$$
where $a, x_0$, and $s$ are positive constants and $d z$ is a Wiener process. What is the process followed by the bond price?