Here i did the work, hope this helps in any way
2,_,_,_,_,6000 r= ?
Lets try each letter,
A,
R= 6 sp 2*6 = 12
2,12
12*6 =72
2,12,72
72*6 = 432
2,12,72,432,
432*6 = 2592
2,12,72,72,2592
2592* 6 = 15552
So this one isnt true
B,
R = 5
2*5 = 10
2,10
10*5=50
2,10,50
50*5 = 250
2,10,50,250
250*5 = 1250
2,10,50,250,1250
1250*5 = 6250
So It isnt B either
C,
R = 5
This one isnt true since it follows the last one but with multiplying error.
That leaves us with D,
R = 4
2*4 =8
2,8
8*4 = 32
2,8,32
32*4 = 128
2,8,32,128
128*4 = 512
2,8,32,128,512
512*4 = 2048
2048* 4 = 8192
So D is no it.
Answer: I dont know, none of these adds up.