Physics: Energy of a Spring--Harmonic Motion?

An object of mass m attached to a spring of force constant k oscillates with simple harmonic motion. The maximum displacement from equilibrium is A and the total mechanical energy of the system is E.

What is the system's potential energy when its kinetic energy is equal to (3/4)E? (multiple choice question)

And the choices are:

kA^2

(kA^2)/2

(kA^2)/4

(kA^2)/8

According to the formula in the book, E=(1/2)kA^2, so wouldn't (3/4)E=(3/8)kA^2? But it's not one of the choices.

Please help me. Thanks.

**Update:**

Thanks BluePhysicsTea for Part I, here's the other part of the problem:

What is the object's velocity when its potential energy is (3/4)E?

+-(sqrt(k/m))A

+-(sqrt(k/m))(sqrt(2/3))A

+-(sqrt(k/m))(A/sqrt(3))

+-(sqrt(k/m))(A/sqrt(6))