PIsarenko Harmonic Decomposition method for PSD estimation
Since you have $v_{min}$, the eigenvector corresponding to the minimum eigenvalue, compute the function $\hat{P}_{PHD}(e^{j\omega})$. 

The vector $e$ is given by $e = [1 \quad e^{j\omega} \quad e^{2j\omega} \ldots e^{pj\omega}]$

Make a plot of $\hat{P}_{PHD}(e^{j\omega})$ and measure the $p=3$ peaks to find the frequencies.