The student is conducting a nutrition experiment using lab rats. One group (control group) is fed a normal diet, while the other group (experimental group) is fed a diet high in protein. There were 30 rats total used in the experiment. At the end of the experiment, the average mass (weight) of a rat in the control group was 60.4 g while the average mass (weight) of a rat in the experimental group was 0.0689 kg. What is the average difference in weight between the two groups in grams?