OO arctan n 4. (a) Using direct comparison test, determine whether the series E is convergent. Be sure to n=1 n2 + 1 clearly state a general term bn of the comparing series (that is, bn = ?). If the series is not convergent, write DNE. If the direct comparison test is inconclusive, you may use another test.(b) Using limit comparison test, determine whether the series ) n (n + 1 ) (n + 2 ) ( n + 3 ) is convergent. n=1 Be sure to clearly state a general term on of the comparing series (that is, bn =?). If the series is not convergent, write DNE. If the limit comparison test is inconclusive, you may use another test