Let $B_t$ be a 1-dimensional Brownian motion and $t \in [0,T]$. Suppose we have a diffusion process $X_t$ such that $$ dX_t = u(X_t,t) dt + v(X_t,t) dt \hspace{10pt} \text{ and } \hspace{10pt} X_0= x \in (a,b) \subset \mathbb{R}$$ for some smooth $u$ and $v$. Let $\tau(x,t) = \inf \big\{ s \in [t,T]: X_s\notin (a,b) \big\}$ be the first exit time. Is there any method to computeobtain some estimate about the derivative $\dfrac{\partial \tau}{\partial x}$?expectation of different quotient of (suppose it exists$\dfrac{\tau(x+h) - \tau (x)}{h}$?) I can not find it some standard textbooks.