The parabola with equation y = 4 – x² intersects the positive x-axis at Q and the y-axis at P.

The straight line L₁ has gradient m and passes through P, and the straight line L₂ which passes through Q, is parallel to L₁.

L₁ intersects the parabola at S and L₂ intersects the parabola at R.

Given that m > 0, find an expression for the area of the trapezium PQRS in terms of m.

What if m < 0?