An observational study is conducted to compare experiences of men and women between the ages of 5059 years, following coronary artery bypass surgery. Participants undergo the surgery and are followed until the time of death, until they are lost to follow-up, or up to 30 years, whichever comes first. The following table details the experiences of participating men and women. The data below are years of death or years of last contact for men and women.

Men		Women
Year of Death	Year of Last Contact		Year of Death	Year of Last Contact
5	8		19	4
12	17		20	9
14	24		21	14
23	26		24	15
29	26			17
	27			19
	29			21
	30			22
	30			24
	30			25
				30

a) Estimate the survival functions for each treatment group using the Kaplan-Meier approach.

b) Test whether there is a significant difference in survival between treatment groups using the log rank test and a 5 percent level of significance.

Please answer both a and b for this question and show step by step on how to solve the problem.