you don't need that info
8c is unrecaptured 1250 gain which is included in the 1231 gain on line 9. don't worry you're not doubling up
the 1250 gain will be tax at one rate while the remainder (1231 gain less 1250 recap) gets in effect tax at a different rate
15b is the adjustment to the gain or loss (line9) for alternative minimum tax purposes. there is no adjustment for 8c
so just enter everything as shown in part III and you'll be fine.
