To find the total area available for printing, we need to subtract the area of the margins from the total area of the pages.

The total area of the pages can be calculated by multiplying the length and width of each page and then multiplying by the total number of pages:

Total area of pages = (20 cm - 2 * 2.5 cm) * (14 cm - 2 * 2 cm) * 360 pages = (20 cm - 5 cm) * (14 cm - 4 cm) * 360 pages = 15 cm * 10 cm * 360 pages = 150 cm * 360 pages

To convert the area from square centimeters to square millimeters, we need to multiply by 100 (since 1 cm = 10 mm):

Total area of pages = 150 cm * 360 pages * 100 mm/cm = 150 * 360 * 100 mm^2 = 5,400,000 mm^2

Therefore, the total area available for printing is 5,400,000 mm^2, which is equivalent to 51840 cm^2.