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Suppose we have a language using the reference model ie all variables are references, there is no explicit dereference operator). Memory is freed by a reference-counting garbage collector. Consider the following program. State which variables point to which objects after the execution of each line of the program and what the values of the reference counters of each object are (you can show only the information that changed during the execution of the line). Which objects can be garbage-collected after the execution of the last line? type C = type D = record {C f; ); C c1 = new C; C c2: D d1 = new D; D d2 = new D; % 01 is allocated (and cl initialized to point to ol) % (e2 is initialized to null) % o2 is allocated (and d1 initialized to point to 02) % 03 is allocated d1.f = c1; c2 = c1; c1 new C; d1.f = c1; d2.f = c2 ; e2 = null; % 04 is allocated