School of Mathematics and Statistics, University of Sydney, New South Wales, Australia and Melanoma Institute Australia, Sydney, New South Wales, Australia.|School of Mathematics and Statistics, University of Sydney, New South Wales, Australia and Melanoma Institute Australia, Sydney, New South Wales, Australia.|School of Mathematics and Statistics, University of Sydney, New South Wales, Australia and Melanoma Institute Australia, Sydney, New South Wales, Australia.|School of Mathematics and Statistics, University of Sydney, New South Wales, Australia and Melanoma Institute Australia, Sydney, New South Wales, Australia.