题目如下，AR=abnormal return.对event study很不熟悉，想请教这类问题如何用stata解决？思路即可，stata代码更好，先谢过小伙伴们。[size=12.000000pt]Given the following information for an event study in Table 6.1:

(a)  Calculate AR based on the constant-mean-return model.

(b)  Calculate the cross-sectional t-test statistic and test the null hypothesis that E[AR0] = 0.

(c)  Calculate the traditional t-test statistic and test the null hypothesis that E[AR0] =0。