* @param unit The <code>Unit</code> to change the work type of.
     * @param type The new <code>GoodsType</code> to produce.
     * @return An <code>Element</code> encapsulating this action.
     */
    public Element changeWorkType(ServerPlayer serverPlayer, Unit unit,
                                  GoodsType type) {
        if (unit.getWorkType() != type) {
            unit.setExperience(0);
            unit.setWorkType(type);
        }

        // Private update of the unit.
        return new ChangeSet().add(See.only(serverPlayer), unit)
            .build(serverPlayer);
    }