There seems to be an error in exercise 32.1.3

[bluestyle97]

The answer to exercise 32.1.3 says that "then we can get the T(time) = (n-m+1)*[a(1)*b(1)+a(2)*b(2)+,,,+a(m)*b(m)] So we get the answer.", but after I sum up the series, I find that the result is

(1-d^(-m))/(1-d^(-1))-m/d^(-m)

, instead of expected result

(1-d^(-m))/(1-d^(-1))

, so I think that this answer is not correct.