What is the relationship between the standard cell potential

What is the relationship between the standard cell potentials, E, for the following two galvanic cell reactions?

I. 2Ag^+(aq) +Sn^(2+)(aq)=Sn^(4+)(aq) +2Ag(s)

II. Ag(s) +1/2Sn^(4+)(aq)=1/2Sn^(2+)(aq) +Ag^(+)(aq)

Answer: A). E(I)=E(II) B). E(I)=2E(II) C). E(I)= -E(II) D. E(1) = -2E(II)

PLEASE HELP TO EXPLAIN ANSWER. THANK YOU.

Solution

C). E(I)= -E(II)