$(3)$ Explain $($briefly$)$ why each of the following integrals is improper. YOU DO NOT NEED TO EVALUATE THEM!!

$($a$){\displaystyle \underset{2}{\overset{}{}}}{e}^{-3p}dp$

$($b$){\displaystyle \underset{-2}{\overset{3}{}}}\frac{1}{x^4}dx.$

$(4)$ Use the comparison principle to determine if the following improper integral converges. If the integral converges, find an upper bound for its value.

${\displaystyle \underset{1}{\overset{}{}}}\frac{5-sin(t)}{t^3}dt$