Where an employee in a single workweek works at two or more different types of work for which different straight-time rates have been established, the regular rate for that week is the weighted average of such rates. That is, the earnings from all such rates are added together and this total is then divided by the total number of hours worked at all jobs. Such an employee may agree with his or her employer in advance to be paid overtime for the type of work that is performed during the overtime hours. An example of this might be a school librarian who also works part of the week as a teacher’s aide at a different rate of pay. The regulations on this topic are found at 29 C.F.R. §§ 778.115 and 778.419.