Shown below are the 30 survival times (months) of 30 melanoma patients, 11 of which were treated with the immunotherapy BCG and 19 treated with the immunotherapy c. parvum. The "+" indicates censoring. BCG: 3.9 5.4 7.9 10.5 16.6+ 16.9+ 17.1+ 19.5 23.8+ 33.7+ 33.7+ c parvum: 6.9 7.7 7.8+ 8.0 8.2+ 8.2+ 8.3 10.8+ 11.0+ 12.2+ 12.5+ 14.8+ 16.0+ 18.1+ 21.4+ 23.0+ 24.4 24.8+ 26.9+ a. Estimate the survival curves for each treatment using the Kaplan-Meier method by hand