Acertain half-reaction has a standard reduction potential . an engineer proposes using this half-reaction at the anode of a galvanic cell that must provide at least of electrical power. the cell will operate under standard conditions. note for advanced students: assume the engineer requires this half-reaction to happen at the anode of the cell.

An electrochemical cell are of two types 1) Chemical 2) concentration

For the present application, since the engineer requires this half-reaction to happen at the anode of the cell, chemical cell must be preferred. Further since, the engineer required, the emf of cell equal to half cell reaction, the counter electrode/electrolyte that can be used is Pt/H2/H+. It must be noted that std reduction potential of this electrode is 0v. It must also be noted that, engineer requires this half-reaction to happen at the anode of the cell. Oxidation occurs at anode compartment. Hence, the remaining half cell should comprise of chemical, whose std. oxidation potential is higher than that of Pt/H2/H+ or std.  reduction potential is less that that of Pt/H2/H+. For, this purpose, those chemicals must be chosen, which are placed below H2/H+ in electrochemical series. If this material is of the form X/X+, the cell representation of the overall electrochemical cell is
X/X+//H+/H2/Pt

What are the options? i can you if you give them.

Ithink its called the coefficent.