一道融资租赁，求PV of lease payment的题 看不懂

A regional jet manufacturer delivers 20 regional jets to an airline under long-term leases. The lease terms are for 15 years with annual payments of $5 million per plane; the first payment is due on delivery. The company classifies the leases as finance leases and prepares its financial statements according to US GAAP. The company usually sells these jets for $45 million each, with production cost averaging $40 million per jet. In the year in which the leases are signed, if an interest rate of 7% is used to determine the present value of the lease payments on the deal, the gross profit on this transaction will be closest to:

• $175 million.
• $100 million.
• $111 million
  

The first lease payment is due on delivery; hence the leases are annuities due.

The present value (PV) of the lease payments on a per-plane basis is:

PV of an annuity due, 15 annual payments of $5 million at 7% = 48.727

答案关于PV的计算没看懂，N=15， PMT=5 ，I=7 ？ PV为什么就等于48.727


求大神，指点！