13. A company is offering a perpetuity you can purchase for retirement. If the perpetuity starts 40 years from today and pays $50,000 per year, which formula correctly gives the PV if r = 4%?

(a) PV = 50,000 x [(1/.04) - (1/(.04 x 1.0440))] x(1.0440)

(b) PV = 50,000/(1.0440)

(c) PV = 50,000 x 40

(d) none of the above

why choose D?plz explain step by step,thank you so much!