Calculate the IRR when given terminal growth rate?

Hi,

How should the IRR be calculated with the following information?

Cash flows:
Year 0 ($500k)
Year 1 $10k
Year 2 ($50k)
Year 3 $5k
Year 4 $20k
Y5 onwards 50k (with terminal growth rate of -5%)

and discount rate of 15%.

Any help is very much appreciated.
Thanks.