How do you handle the costs for different time types when using Resource Groups and Job Rate Management?

For example, we have a Resource Group ‘Engineers’ which allow you to add one cost value and sales part value.  We then assign work to engineers within that resource group via Mobile Work Order.

When the engineer books their time they select one of the following time types - Standard, 1.5x, 2x, depending on their contractual hours.

How does the costs associated with those time types get added to the work order if the resource group only has one cost assigned to it?  Similarly, how does the sales part relating to the time type get added to the work order to ensure the customer is charged the appropriate rate?