Suppose y=y(x) be the solution curve to the differential equation (d y)/(d x)-y=2-e^-x such that lim_x → ∞ y(x) is finite. If a and b are…

Suppose $\displaystyle y=y(x)$ be the solution curve to the differential equation $\displaystyle \frac{d y}{d x}-y=2-e^{-x}$ such that $\displaystyle \lim _{x \rightarrow \infty} y(x)$ is finite. If $\displaystyle a$ and $\displaystyle b$ are respectively the $\displaystyle x$ - and $\displaystyle y$ - intercepts of the tangent to the curve at $\displaystyle x=0$, then the value of $\displaystyle a-4 b$ is equal to \_\_\_\_.