Answer: The fraction would be 0.53.
Step-by-step explanation:
Since we have given that

where, A is the constant initial production rate
t is the time.
For 98 years, the production rate in motorcycles per year would be

For 13 years, the production rate in motorcycles per year would be

So, the fraction of their total production was built during the last 13 years would be

Hence, the fraction would be 0.53.