A uniform electric field of magnitude \(E = 400 \text{ N/C}\) is directed in the positive \(x\)-direction. A small particle with charge \(q = +2.0 \text{ }\mu\text{C}\) is moved at a constant speed by an external agent along a curved path from point \(A (0 \text{ m}, 0 \text{ m})\) to point \(B (0.30 \text{ m}, 0.40 \text{ m})\). The total path length traveled by the particle is \(0.80 \text{ m}\). What is the work done on the particle by the external agent?