本人痛苦的自学计量和sas，伍德里奇的书看了挺多但课后计算机习题还没怎么做

最近抓紧解决习题，却现在卡在一道很简单的题上，周围没人学计量和sas，都不知道该怎么弄

于是上论坛请前辈赐教：

计量经济学导论现代观点第三版第四章习题

4.14 Refer to Problem 3.14. Now, use the log of the housing price as the dependent
variable:
log(price) ＝b0 +b1*sqrft +b2*bdrms+ u.
(i) You are interested in estimating and obtaining a confidence interval for
the percentage change in price when a 150-square-foot bedroom is
added to a house. In decimal form, this is  c1=150*b1+b2

原式有b0,b1,b2,三个参数，现在引入c1这个参数，使得c1＝150*b1+b2,然后估计c1的值；我把b2用c1,b1替换，用sas输入

proc model data=homework.hprice2;
parm b0 b1 c1;
lprice=b0+b1*(sqrft-150*bdrms)+c1*bdrms;
fit lprice/ols;
run;

 命令怎么都弄不出结果，请问应该输入什么代码呢（我刚开始自学，还不太会用）