  This paper is concerned with identification of a spatial source function from
final time observation in a bi-parabolic equation, where the full source
function is assumed to be a product of time dependent and a space dependent
function. Due to the ill-posedness of the problem, recently some authors have
employed different regularization method and analysed the convergence rates.
But, to the best of our knowledge, the quasi-reversibility method is not
explored yet, and thus we study that in this paper. As an important
implication, the H{\"o}lder rates for the apriori and aposteriori error
estimates obtained in this paper improve upon the rates obtained in earlier
works. Also, in some cases we show that the rates obtained are of optimal
order. Further, this work seems to be the first one that has broaden the
applicability of the problem by allowing the time dependent component of the
source function to change sign. To the best of our knowledge, the earlier known
work assumed the fixed sign of the time dependent component by assuming some
bounded below condition.
