Yes, overtime in CA is more than 8 hours in a day or 40 in a week.
Under both CA law, and federal wage laws, it is legal for an employer to pay different wages depending on the work being done by the employee. In fact there are even rules designed so that the employer and employee know how overtime worked should be paid when an employee works at two different tasks, and for differing hourly wages for each task.
When an employee works at two different jobs, and is paid at different wage rates for each job, the employer has two choices as to how to pay overtime.
The first is the weighted average
. Using this method, the employee is paid overtime based on the weighted average of their non-overtime wage rates. If the number of hours worked at each pay rate varies from week to week, then this average must re-calculate this each week.
The second method is for you and your employer to agree, preferably in writing, that you will receive overtime at a rate not less than one and one-half times the hourly non-overtime rate applicable for the type of work
performed during each
overtime hour they work at that job.
Here is a great explanation of the process used in CA: http://www.calemployeerightsblog.com/2007/02/19/overtime-calculation-with-two-different-hourly-rates/
You of course are free to quote a piece rate for each job---so long as he is paid at least minimum wage based on the hours worked.
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I wish you the best in 2012.