Fixes to HW2

Thanks to a comment by a student, we have noticed a small error in the second assingment. Thus a few adjustments have been made to questions 3-5 in the dry part. We further changed the formula relating $p_L\left(\bb{x}\right)$ and $p_H\left(\bb{x}\right)$ from $p_H\left(\bb{x}\right)=\alpha p_L\left(\alpha\bb{x}\right)$ to $p_H\left(\bb{x}\right)=\alpha^2 p_L\left(\alpha\bb{x}\right)$.
We will not reduce any points for submissions which match the previous version of the assignment and ignore these errors.