Costing system, which is a combination of process costing and job costing system is classified as

weighted costing system
average costing system
hybrid costing system
double costing system

The correct answer is C. hybrid costing system.

A hybrid costing system is a combination of two or more costing systems. It is used when the costing requirements of a particular product or service cannot be met by a single costing system. The most common type of hybrid costing system is a combination of process costing and job costing.

Process costing is a costing system that is used for products or services that are produced in large quantities. In process costing, costs are accumulated by process or department and then assigned to units of product or service using a predetermined cost per unit.

Job costing is a costing system that is used for products or services that are produced in small quantities or that are customized for individual customers. In job costing, costs are accumulated by job and then assigned to units of product or service using actual costs.

A hybrid costing system can be used to improve the accuracy of product costing. For example, a hybrid costing system could be used to assign costs to products that are produced in both large and small quantities. In this case, the costs of the large-quantity products could be assigned using process costing, and the costs of the small-quantity products could be assigned using job costing.

A hybrid costing system can also be used to improve the efficiency of product costing. For example, a hybrid costing system could be used to assign costs to products that are produced in a continuous process. In this case, the costs of the continuous process could be assigned using process costing, and the costs of the individual units of product could be assigned using job costing.

The main advantage of a hybrid costing system is that it can provide a more accurate and efficient way of costing products than a single costing system. The main disadvantage of a hybrid costing system is that it can be more complex to implement and use than a single costing system.