The maximum & minimum number of sources that can be multiplexed so that no data loss occurs on TOKEN BUCKET?
A is correct. As 1st part is already described i will explain derivation of S2 only. 
Let there are N stations. When buffer is added then even when source is off, data will persist so considering duty cycle here we say that the actual data transmitted per unit time during the whole duty cycle is (1/3)10 [for 1 unit of on-time data is transmitted and for another 2 unit of off-time it stays in buffer so in 3 unit time 10Mbps data is tranferred]. This is the case will all other N-1 stations also. So adding all should be = Max capacity of channel.
N(1/3)*10 = 100
N=30