You are given the coordinates of two axis-aligned rectangles in a 2D plane. Your task is to calculate the total area covered by both rectangles.

• The first rectangle is specified by the coordinates of its bottom-left corner (ax1, ay1) and top-right corner (ay1, ay2).

• Similarly, the second rectangle is defined by its bottom-left corner (bx1, by1) and top-right corner (bx2, by2).

Note: The rectangles may overlap.

Constraints:

• $-10^4 \leq$ ax1 $\leq$ ax2 $\leq 10^4$

• $-10^4 \leq$ ay1 $\leq$ ay2 ...