SAS期权定价 程序求助

以下是B-S模型的程序 ，想要给r s t 这些变量定个数 比如r=0.05 该怎么写？程序的开头怎么写？

start price_c (r,sigma,t,s,x);
d1=(log(s/x)+(r+sigma##2/2)*t)/(sigma*sqrt(t));
d2=d1-sigma*sqrt(t);
c=s*cdf('normal',d1)-x*exp(-r*t)*cdf('normal',d2);
return(c);
finish price_c;
print c;

1. proc iml;
   
2. start price_c (r,sigma,t,s,x);
   
3. d1=(log(s/x)+(r+sigma##2/2)*t)/(sigma*sqrt(t));
   
4. d2=d1-sigma*sqrt(t);
   
5. c=s*cdf('normal',d1)-x*exp(-r*t)*cdf('normal',d2);
   
6. return(c);
   
7. finish price_c;
   
8. c = price_c(.05, .3, 1/12, 100, 120);
   
9. print c;
   
10. quit;

复制代码

where r=risk-free interest rate, sigma=implied volatility, t = time to expiration in years, s=current price, x = strike price.

顶个

现在急需要这个啊，换个问题：怎么用SAS调用这个程序啊？说得具体点！！！急需！！！