are my assumptions wrong

i read on here plenty of calculations but i dont get it.
my assumptions
1/ 11/12 fin year 8.3 m pounds
2/ cash at june 30 117.4 m
3/ draw down of $135m cash from the debt facility
4/ so total cash on hand $252.4m
5/ debt due $40 m so wont need to be refinanced cash now reduced to $212m
6/total debt $630m + $135m = $765 @ 8.6% = $65.79m interest
7/ corporate costs $40m
8/ royalities $15m
9/ 8.3 m p split say 50% spot and 50 long term
10/ spot US$ 54.00/p long term $62.00/p
11/4.15 m @ $54 = $224.1m
12/4.15mp @ $62.00 = $257.3m say total rev = $481.4m
13/ costs @ $35/p = $290.5

so

total revenue $481.4m

mining costs @ $35/p $290.5
corporate cost $ 40.0
royalities $ 15.0
interest $ 65.8
total costs $411.3

$ 70.1

depreciation $ 36.0

profit before tax $ 34.1

tax at 30% $ 10.23

profit after tax $ 23.87



Cash than = $212.0 m
profit $ 23.87
depreciation$ 36.0


Total cash end of 11/12 fin year $$271.87

my assumptions are that pdn still makes a profit at these low levels and can afford to pay its debts


please let me know your ideas