4. (There are two problems under this item.) Find the exact values of the following denite integrals (do not approximate). 1 81: d (a) [0 9+4e22' 5\" (b) ff: 5. _ (There are two problems under this item.) Determine whether each improper integral converges or diverges. If it converges, nd its exact value. +oo 1/:L'2 (a) f e 3 d2: 1 112 0 2