How do I calculate the late start and late finish calculations?

Activity	Duration	ES	EF	LS	LF	SLACK	CRITICAL
A	27	0	27	0	27
B	55	27	82
C	65	27	92
D	56	92	148
E	40	82	122
F	1.5	122	123.5
G	26	148	174
H	25	174	199
I	30	199	229
J	10	199	209
K	1	209	210
L	30	229	259