Here is a work schedule for a work week defined as Monday - Sunday.
These are for hours worked in California.

Monday 8 hours
Tuesday 8 hours
Wednesday 8 hours
Thursday 7.75 hours
Friday 8 hours
Saturday 10 hours

Should the hours on Saturday be calculated as:
a. 0.25 regular, 8 overtime and 1.75 double time
b. 0.25 regular, 9.75 overtime

Thanks

It should be calculated as per your first example "a"

Can you explain why.
According to the calif labor law, double time is for all hours work in excess of 12 hours in any workday and for all hours worked in excess of eight on the seventh consecutive day of work in the workweek.
The 10 hours on the sixth day does not meet either one of these requirements.

After looking at it again, you are right. The correct answer is "b"

Here is the law:
Overtime Laws
http://www.workforcesoftware.com/labor-laws/ca_laws.html#ot_laws

For more than 8 hours in a day, an employee must be paid 1.5 times his or her usual rate, and for over 12 hours in a day must be paid twice the standard rate. In addition, if an employee works 7 consecutive days, they must be paid 1.5 times the usual rate for the first 8 hours, and doubletime for any hours over 8. The 7th consecutive day law applies regardless of how many hours an employee worked in the preceding six days. Also, any hours over 40 in a week must be paid at time and a half