NOTE – For maximum number of level or height there will be minimum number of keys in each node which in this case 5 so this makes number of pointers 6
Blocks required = 1250/3 = 417
Level 1 = floor(417/5) = 83
Level 2 = floor(83/6) = 13
Level 3 = floor(13/6) = 2
Level 4 = floor(2/6) = 1
So, total no. of levels = 4