T&M labor schedule rates

Hello,

Where are the T&M laboe scheudle rates ratio is stored from which Charges uses the same for calculating the extended price based on the ratio. like example Double rate - 2x normal rate, overtime - 1.5x normal rates (with no contracts defined).

For example if the normal rate (price for labor item) is $100, i expect Charges to show 200$ automatically whenever it splits & calculates for double rate time. Pls suggest.

Mohana