问题如下图：
老师你好，这题请问怎么理解？
NO.PZ2020021203000072问题如下A four-month Europecall option on a stois currently selling for US2.50. The current stopriis US54, anthe strike priis US50. A vinof US1.50 is expectein one month. The risk-free interest rate is 3% per annum (annually compoun for all maturities. Whopportunities are there for arbitrageur? The lower bounfor the option priisS−PV(K)−PV(vs)=54−501.031/3−1.51.031/12=2.99S-PV(K)-PV(vs)=54-\frac{50}{1.03^{1/3}}-\frac{1.5}{1.03^{1/12}}=2.99S−PV(K)−PV(vs)=54−1.031/350−1.031/121.5=2.99The option is selling for less thits lower boun arbitrageur cbuy the option anshort the stofor initicash inflow of US51.50. The arbitrageur hto pvin of US1.50 after one month.If the option is exercise the cost of closing out the short position will USO 50. If it is not exercise the cost of closing out the short position will less thUS50. The worst-case scenario for the arbitrageur is therefore:Toy: +51.50,One month: -1.50, anour months: -50.00.When the scount rate is zero, the sum of these cash flows will have zero present value. Any positive scount rate gives a positive sum of present values.If option is exercise the cost of closing short position is 50是什么意思啊
NO.PZ2020021203000072 问题如下 A four-month Europecall option on a stois currently selling for US2.50. The current stopriis US54, anthe strike priis US50. A vinof US1.50 is expectein one month. The risk-free interest rate is 3% per annum (annually compoun for all maturities. Whopportunities are there for arbitrageur? The lower bounfor the option priisS−PV(K)−PV(vs)=54−501.031/3−1.51.031/12=2.99S-PV(K)-PV(vs)=54-\frac{50}{1.03^{1/3}}-\frac{1.5}{1.03^{1/12}}=2.99S−PV(K)−PV(vs)=54−1.031/350−1.031/121.5=2.99The option is selling for less thits lower boun arbitrageur cbuy the option anshort the stofor initicash inflow of US51.50. The arbitrageur hto pvin of US1.50 after one month.If the option is exercise the cost of closing out the short position will USO 50. If it is not exercise the cost of closing out the short position will less thUS50. The worst-case scenario for the arbitrageur is therefore:Toy: +51.50,One month: -1.50, anour months: -50.00.When the scount rate is zero, the sum of these cash flows will have zero present value. Any positive scount rate gives a positive sum of present values. When the scount rate is zero, the sum of these cash flows will have zero present value. Any positive scount rate gives a positive sum of present values.麻烦讲解下这几句，谢谢
NO.PZ2020021203000072 请问这道题的操作过程怎么理解？
NO.PZ2020021203000072 是strike price加vin？为什么是这两个数相加啊？
