Time costs for pushdown stacks. Justify the entries in the table below, which shows typica...

Time costs for pushdown stacks. Justify the entries in the table below, which shows typical time costs for various pushdown stack implementations, using a cost model that counts both data references (references to data pushed onto the stack, either an array reference or a reference to an object’s instance variable) and objects created. Assume that the Integer objects are not cached (so they must be created for each push).