Consider the SDE $$dr_t = (b-ar_t)dt +\sigma dW_t, \text{with } a; b > 0.$$ Let $$F(t; r) = E(\exp(-\int_{t}^{T}r_sds)| r_t = r).$$ (F can be interpreted as price of a zero coupon bond with maturity T.)
Use the Feynman-Kac formula to derive a PDE for the function $F(t; r)$.
I wanted to use Ito to obtain formula for $r_t$ and then plug it into Feynman-Kac formula $$E_{t0,x}=(\exp(-\int_{t}^{T}r(s,X_s)ds)\phi(X_t))$$ from the lecture, but I can't derive it. Any help is greatly appreciated