Determine the intervals where h{t] : 2 arctan(t) is concave up and concave down. Q Concave up on [00, co} concave down nowhere O Concave up nowhere} concave down on [00, co] 0 Concave up on [[11 co} concave down on {00, U) Q Concave up on [oo, 0'), concave down on (0, 00) O Concave up on [00, 2), concave down on (2, co}