The charge density of the sheet is 1.384×10⁻⁷C/m².
Charge density is defined as the charge per unit area.
The sheet is a square of length l=17 cm.
Calculate the area A of the sheet .

The charge Q on the sheet is

The charge density σ is given by,

Substitute 4×10⁻⁹C for Q and 0.0289 m² for A.

Thus, the charge density of the sheet is 1.384×10⁻⁷C/m².