As a result, the left hand side of Eq. (13) has a maximum at the point
t2 ¼ ~t2, and is s c þ c3 þ c2
d exphc2þdðsc2 cþc3Þi. To find the value of
(t1, t2) such that TP(t1, t2) in Eq. (8) has a maximum value, we consider
the following two cases: (i) bs (i + b + h)cP0 and (ii)
bs (i + b + h)c < 0.