Final answer:
Over the next 50 million years, 3,150,000 km of plate will be subducted.
Step-by-step explanation:
The rate of subduction, or convergence, is given as 63 mm/yr. To calculate the amount of plate subducted over 50 million years, we can multiply the convergence rate by the time period:
63 mm/yr * 50 million yr = 3,150 million mm = 3,150,000 km
Therefore, over the next 50 million years, 3,150,000 km of plate will be subducted.