Answer:
rate = 6.3235%
At a market rate of 6.3235% this will be  a fair deal
Explanation:
under perpetuities the principal is never redeem. the investor receive cash payment for an indefinite period of time
This means:
perpetuities  present value = C/r
where:
C= annual payment
r= rate
680,000 = 43,000/rate
43,000/680,000 = rate
0.06323529 = rate
rate = 6.3235%