The sixth term of an arithmetic series is 12. The sum of the first 16 terms of the series is SnS_nSn and S16=152S_{16} = 152S16=152. Find the first term and common difference of the series.
A second arithmetic series has first term −4-4−4 and common difference 12\frac{1}{2}21. The sum of the first nnn terms of this series is TnT_nTn. Find the value of nnn such that Tn=SnT_n = S_nTn=Sn, where n>0n > 0n>0.