Answer:
The answer is 20.5 years.
Step-by-step explanation:
If we assume that there is compound interest, we can calculate the increase of the spending on equipment with an annual interest of 9% which results in the $476,374 of the $500,000 being spend on equipment in the 20th year and $519,248 being spend in the 21st year. So between the year 20 and 21, the equipment funding will be reduced to zero.
I hope this answer helps.