Let the mean and the variance of 5 observations $x _ { 1 } , x _ { 2 } , x _ { 3 } , x _ { 4 } , x _ { 5 }$ be $\frac { 24 } { 5 }$ and $\frac { 194 } { 25 }$ respectively. If the mean and variance of the first 4 observation are $\frac { 7 } { 2 }$ and $a$ respectively, then ( $4 a + x _ { 5 }$ ) is equal to\\
(1) 13\\
(2) 15\\
(3) 17\\
(4) 18