Question $4[4$ marks$]$

Use the master method to give tight asymptotic bounds for the following recurrences $($if the

master method cannot be applied give your argument$)$:

$($a$)$ marks$]T(n)=4T(\frac{n}{2})+n^{2}lgn.$

$($b$)$ marks$]T(n)=6T(\frac{n}{2})+n^3.$