a) Endwert = 5280·1.041·(1.04134 - 1) / 0.041 ≈ 391503,50 also nein
b) Barwert = 391503.50 / 1.04134 ≈ 99864,43 also nein
c) 391503.50·1.04120 - b ·(1.04120 - 1) / 0.041 = 0
→ b ≈ 29063,18 also nein
d) 391503,50 ·1.033t - 31544·(1.033t - 1) / 0.033 = 0
→ t ≈ 16,23 also ja
e) 31544 = 391503,50 · x
→ x ≈ 0.08157 → r ≈ 8,16 % also nein
Edit: zu e) Zahlung ist vorschüssig,
also 31544 = (391503,50 - 31544) · x
→ r = 8,76 (vgl. Kommentar Mathecoach)
Gruß Wolfgang