We have the following model for the short rate $r_t$under $\mathbb{Q}$:
$$dr_t=(2\%-r_t)dt+\sqrt{r_t+\sigma_t}dW^1_t\\d\sigma_t=(5\%-\sigma_t)dt+\sqrt{\sigma_t}dW^2_t$$
What is the PDE of which the solution gives the price of the floorlet with the following payoff in $t=1$:
$$X=0.5\bigg[ 2.5\%-L(0.5,1) \bigg]^+$$
where $L(0.5,1)=(P(0.5,1)^{-1}-1)\frac{1}{0.5}$ is the linearly compounded rate from $0.5$ to $1$.