Calvin cycle energy expenditure

The Calvin-Benson cycle and the pentose phosphate pathway (Eq. 17-12) have many features in common but run in opposite directions. Since the synthesis of glucose from C02 requires energy, the energy expenditure for the two processes will obviously differ. Describe the points in each pathway where a Gibbs energy difference is used to drive the reaction in the desired direction. 

Note that 30 molecules of ATP are consumed per hexose molecule formed when the C4 pathway delivers CO2 to the Calvin cycle, in contrast with 18 molecules of ATP per hexose molecule in the absence of the C4 pathway. The high concentration of CO2 in the bundle-sheath cells of C4 plants, which is due to the expenditure of the additional 12 molecules of ATP, is critical for their rapid photosynthetic rate, because CO2 is limiting when light is abundant. A high CO2 concentration also minimizes the energy loss caused by photorespiration. 

What is the energy expenditure for synthesizing a hexose Six rounds of the Calvin cycle are required, because one carbon atom is reduced in each round. Twelve molecules of ATP are expended in phosphorylating 12 molecules of 3-phosphoglycerate to 1,3-bisphosphoglycerate, and 12 molecules... 

---