# Finding Dual Objective

I have the following simplified optimization problem:

$$max \quad ax+by$$

S.t.

$$0≤x≤\bar{X}$$

$$0≤y≤\bar{Y}$$

$$z=E−x+β.y$$

where, $$E$$, $$β$$, $$a$$, $$b$$, $$\bar{X}$$, $$\bar{Y}$$ are parameters and the rest are variables. What would be the dual objective function for this optimization problem?