Well i was thinking of the orientation shouldn't it be like -6.4% see:
Profit % = mp(adown(down)+aup(up))/p(mg(down)-ma(down)) x 100%
Profit % = mp(adown+aup)/mp (g-a) x 100%
Profit % = (adown+aup)/(g-a) x 100%
Profit % = (2 m/s^2(down) - 2.5 m/s^2(down)) / (9.8m/s^2 (down)- 2 m/s^2(down)) x 100%
Profit % = -0.5m/s^2/ 7.8 m/s^2 x 100%
Profit % = -6.4%