What is the standard cell potential of a cell made of theoretical metals ma/ma2+ and mb/mb2+ if the reduction potentials are -0.19 v and -0.85, respectively?

a) +0.66 V
b) -0.66 V
c) +1.04 V
d) -1.04 V

The activity series is shown in the attached picture. if the element is below the other, then you can displace the other. following the activity series as a guide, the reactions are as follows: nickel and aluminum chloride3 ni + 2 alcl₃  → 3 nicl₂ + 2 albarium and copper bromideba + cubr  →  no reaction because cu is less oxidizable than bapotassium nitrate and aluminum3 kno₃ + al  → al(no₃)₃ + 3 ksodium phosphate and zincnaso₄ + zn  → znso₄ + na