I will simplify the question.......Firstly since the output rate is more than incoming rate, we will calculate the time when the bucket will be empty, that is
capacity +(input rate x S) =(output rate x S)
1+ (10 x S) =(20 x S)
S=0.1 sec .............at this time bucket will be empty, till this time we have transferred data at max rate of 20 MB/sec, thus we have transferred 0.1 x 20 =2 MB , now we have to transfer 10 MB more, since the bucket is empty, now the output rate will be equal to input rate, thus
to transfer 10 MB at speed 10 MB/sec, it will require 1 sec.
Thus ans= 1 + .1 =1.1 sec