What must be done to the following half-reactions before they can be added together?Mn (s) → Mn 2+ (aq) + 2e − Fe 3+ (aq) + 3e − → Fe (s)Double the Mn half-reaction and triple the Fe half-reaction.Add H+ ions to the left-side of the Mn reaction.Triple the Mn half-reaction and double the Fe half-reaction.Double the Mn half-reaction.none of the above