(1) Let the frequency with a score within [70,80] be X. According to the histogram of frequency distribution, there are

(0.0 1+0.0 15×2+0.025+0.005)× 10+x = 1，x=0.3，

So the histogram of frequency distribution is as shown in the figure.

The average score is:. x = 45×0. 1+55×0. 15+65×0. 15+75×0.3+85×0.25+95×0.05 = 7 1。

(2) [40,70] There are 0.4×60=24 students.

There are 0.6×60=36 people in [70, 100], and the possible value of x is 0, 1, 2.

So the distribution list of x is:

Then p (x = 0) = C24C260 = 46295; p(X = 1)= c 124 c 136 c 260 = 144295； P(X=2)=C236C260= 105295。

that is

∴ex=0×46295+ 1× 144295+2× 105295=354295.