14. 记SnS_{n}Sn为等比数列{an}\{a_{n}\}{an}的前nnn项和,若S6=4S3S_{6}=4S_{3}S6=4S3,a2+a5=8a_{2}+a_{5}=8a2+a5=8,则a8=(a_{8}=(a8=( )))