Estimated table size = avg. row length *(1+PCTFREE/100) * num. of rows * (1+fudge /100)

I use PCTFREE 10 when avg growth is 0

PCTFREE = ((future size - initial)*100) / future size

ï set the fudgefactor = 20%

a)

pctfree =  10

92 * ( 1+(10/100)) * 15,789,777 * (1+(20/100))

= 1917510518,88 bytes / 1048576 for megabyte

= 1828.68 MB

b)

PCTFree = ((90 - 81)*100) / 90  = 10

81*(1+(10/100)) * 988722 * (1+(20/100))

= 105714156,24 bytes / 1048576 for megabyte

= 100.81MB

c)

PCTFREE = ((155-125)*100)/155 = 19,3 rounded to 20

125 * (1+(20/100)) * 1887225 * (1+(20/100))

= 339700500 bytes / 1048576 for megabyte

= 323.96MB

all calculations are done with google calculator, blame them for errors at the mathematical part :)