Radius of excircle = 4cm2 = 2cm.

Radius of inner circle = 3.2cm2 =1.6cm.

Cross-sectional area of circular drum = (2? - 1.6? )cm？ ×3. 14=4.52 16cm？

The unfolded plastic wrap has a rectangular cross-section, length (the length of plastic wrap) and width (the thickness of plastic wrap).

Cross-sectional area of drum = cross-sectional area after deployment = =4.52 16cm?

Plastic wrap thickness = area ÷ length = =4.52 16cm? ( 100cm×60)=4.52 16cm？ ÷6000 cm = 0.0007536 cm

= 0.007536 mm

Answer: The thickness of plastic wrap paper is about 0.007536 mm, which is commonly called 0.7536 silk (1 mm = 100 silk).

Good luck, goodbye.

Incidentally, it has nothing to do with the width of plastic wrap of 20 cm.