Pressure is defined as Force per unit Area, so $P = \frac{F}{A}$. For a square plate with side length $l$, the area is $A = l^2$. Therefore, $P = \frac{F}{l^2}$. The maximum percentage error in pressure is given by the formula for propagation of errors in division and powers: $\frac{\Delta P}{P} \times 100 = \frac{\Delta F}{F} \times 100 + 2 \times \frac{\Delta l}{l} \times 100$ Given that the percentage error in force is $\frac{\Delta F}{F} \times 100 = 4\%$ and the percentage error in length is $\frac{\Delta l}{l} \times 100 = 2\%$. Substituting these values into the equation: Percentage error in $P = 4\% + 2 \times (2\%) = 4\% + 4\% = 8\%$.