B3 scientists have determined that peak 4 is 7.0 million years old. the center of the ridge is 0 years old. using transect d, calculate the spreading rate (rate at which the sea floor is spreading). give your answers in km/ million years. be sure to show all your work, hint: calculate the spreading rate on each side of the ridge to get the two half-spreading rates and then add them together to get the full-spreading rate km/million years show your work here: