[填空题]
The fifth term, $u_5$ , of a geometric sequence is 125. The sixth term, $u_6$ , is 156.25.
Find the common ratio of the sequence.
r= .
Find $u_1$ , the first term of the sequence.
$u_1$= .
Calculate the sum of the first 12 terms of the sequence.
$S_{12}$= .
