I just finished this paper
So basically try to think of all possible combinations that would give terms with
From the first part that you calculated
if you multiply this term with
possible terms with
would be
,
, &
The sum of their co-efficient = 48 given in the question
64a- (192X2) + 240=48
64a= 48-240+(192X2)
64a= 192
a=192/64