Four point charges form a square with sides of length d, as shown in the figure. In the questions that follow, use the constant k in place of $\frac{1}{4\pi {\u03f5}_{0}}$.

Part A

What is the electric potential $V}_{\to t$ at the center of the square?

Make the usual assumption that the potential tends to zero far away from a charge.

Express your answer in terms of q ,d, and appropriate constants.

${V}_{\to t}=$

Part B

What is the contribution $U}_{2q$ to the electric potential energy of the system, due to interactions involving the charge 2q ?

Express your answer in terms of q, d, and appropriate constants.

${U}_{2q}=$

Part C

What is the total electric potential energy $U}_{\to t$ of this system of charges? Express your answer in terms of q, d, and appropriate constants.

${U}_{\to t}=$

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