Hi Everyone , 

In this case , you have to use concept of LEAK MAP . But in first you have to perform the following configuration on R3 and R4 -

1. On R3 - You have to summarize all of the routes of R1 and R2 on /16 with the following commands -
2.  With summarization You have to use of concept of LEAK-MAP in which we have to leak the loopbacks of R1 and R2 given in task. The  configuration is following - 

 interface FastEthernet0/0

ip summary-address eigrp 123 1.1.0.0 255.255.0.0 leak-map cisco
 ip summary-address eigrp 123 2.1.0.0 255.255.0.0 leak-map cisco1

Standard IP access list 10
    10 permit 1.1.1.0, wildcard bits 0.0.0.255

Standard IP access list 20
    10 permit 2.1.1.0, wildcard bits 0.0.0.255

route-map cisco1 permit 10
 match ip address 20
route-map cisco permit 10
 match ip address 10
 

CONFIGURATION ON R4 -

We have to perform only a little bit configuration on R4 to perform this task , which is that we have to summarize all of the routes of R1 and R2 on /21 . 

interface FastEthernet0/0

ip summary-address eigrp 123 1.1.0.0 255.255.248.0
 ip summary-address eigrp 123 2.1.0.0 255.255.248.0
 

This is the configuration you have to configure to perform this task . 

Have a nice day .