8. Let "学" and "习" represent two different digits. The product of the four-digit numbers "学学学学" and "习习习习" is a seven-digit number, and its unit and millionth digits are the same as the digit represented by "学". How many two-digit numbers can "学习" represent? $\qquad$
Analysis: The unit and million digits of the product are "xue", so "xi" is 1,
"xue xue xue xue" = "xue" $\times 1111$, "xue xue xue xue" $\times$ "xi xi xi xi" = "xue" $\times 1111^{2}=$ "xue" $\times 1234321$, and since the million digit of the product is "xue", "xue" can only be $2,3,4$; therefore, the two-digit number "xue xi" can represent a total of 3 numbers.