imagine that in a given economy the prevailing inflation is equal to 3% and investors expect to earn a real return of 5%. The government plans to issue inflation protected securities (bonds) with the face value equal to 1000 to mature in 20 years. What is the value of the coupon that such a security should offer to be attractive for investors?

A) 20

B) 80

C) 50

D) None of the above

I would like to know the math process please. Thanks