The current relating to corresponding situations are as follows:
(i) Without any external resistance in the circuit −The current in this case would be maximum, so I1 = 4.2A
(ii) With resistance R1 only −The current in this case will be the second smallest value, so I2 = 1.05 A
(iii) With R1 and R2 in series combination −The current in this case will be minimum as the resistance will be maximum, so I = 0.42 A.
(iv) With R1 and R2 in parallel combination−The current in this case would be the second largest value, so I = 1.4 A.