Answer:
 $16,335.90622 
Step-by-step explanation:
The computation of the additional income earned is shown below:
For 40 years 
Future value = Present value × (1 + rate of interest)^number of years 
= $1,500 × (1 + 0.065)^40
= $18,624.1118 
For 50 years 
Future value = Present value × (1 + rate of interest)^number of years 
= $1,500 × (1 + 0.065)^50
= $34,960.01802 
Now the additional amount is 
= $34,960.01802 - $18,624.1118
= $16,335.90622