Consider the quadratic equation 3x2+kx+12=0, where k is a real parameter.
a. (i) Find the value(s) of k for which the equation has real and equal roots.
b. (ii) Find the range of k for which the equation has no real roots.
c. (iii) For k=−10, state the nature of the roots without solving the equation and give a reason for your answer.