Cloud computing is one of the most disruptive and successful phenomena of the last years. Many companies are exploiting commercially available services provided by Infrastructure as a Service (IaaS) providers that allow to either scale out or in computing capabilities as need changes, through rapid allocation or deallocation of virtual computing and storage resources. IaaS services let users offer fresh applications without the need of managing the underlying infrastructure. In this paper, the system consider a MCC model where multiple brokers assign cloud resources to mobile users. The model is characterized by a heterogeneous cloud architecture and by the heterogeneous pricing strategies of cloud service providers. It includes a public cloud and a cloudlet. The system investigates a competitive strategy, and a compete-then-cooperate strategy as a performance bound. The system formulates a cooperative problem where the objective is to minimize the total average price of all brokers, under the constraint that no broker should pay a price higher than the disagreement price. The system designs a new globally optimal solution algorithm to solve the resulting non-convex cooperative problem, based on a combination of the branch and bound framework and of advanced convex relaxation techniques.