随着我国经济的发展，居民的储蓄存款逐年增长\(.\)设某地区城乡居民人民币储蓄存款\((\)年底余额\()\)如下表：
| 年份 | \(2010\) | \(2011\) | \(2012\) | \(2013\) | \(2014\) |
| 时间代号\(t\) | \(1\) | \(2\) | \(3\) | \(4\) | \(5\) |
| 储蓄存款\(y(\)千亿元\()\) | \(5\) | \(6\) | \(7\) | \(8\) | \(10\) |
\((\)Ⅰ\()\)求\(y\)关于\(t\)的回归方程\( \hat y= \hat bt+ \hat a\)．
\((\)Ⅱ\()\)用所求回归方程预测该地区\(2015\)年\((t=6)\)的人民币储蓄存款．
附：回归方程\( \hat y= \hat bt+ \hat a\)中
\( \begin{cases} \overset{b= \dfrac { \sum\limits_{i=1}^{n}(t_{i}- \overset{ .}{t})(y_{i}- \overset{ .}{y})}{ \sum\limits_{i=1}^{n}(t_{i}- \overset{ .}{t})^{2}}= \dfrac { \sum\limits_{i=1}^{n}t_{i}y_{i}-n \overset{ .}{t} \overset{ .}{y}}{ \sum\limits_{i=1}^{n} t_{ i }^{ 2 }-n \overset{}{t}^{2}}}{a= \overset{ .}{y}-b \overset{ .}{t}}\end{cases}\)．