Answer:
0.2449 or 24.49%
Explanation:
Calculate the IRR if the power company gets a fixed feed-in tariff of $0.25/kWh.
IRR means Internal Rate of Return is given by

Where, FV = Final value ($20)
PV = Present value ($0.25)
N = 20 years
Now put the values

=

= 1.24495742 - 1
= 0.24495742
Converting in percentage :
0.24495742 Ă— 100 = 24.49%
IRR = 0.2449 or 24.49%