Find the Determinant of the Matrix $\left[ \begin{array} { r r } \frac { 1 } { 2 } & 1 \\\\- \frac { 1 } { 2 } & \frac { 3 } { 2 }\end{array} \right]$

Find the determinant of the matrix $\left[ \begin{array} { r r } \frac { 1 } { 2 } & 1 \\\\- \frac { 1 } { 2 } & \frac { 3 } { 2 }\end{array} \right]$ , if it exists

A) $\frac { 3 } { 4 }$

B) $5$

C) $- \frac { 5 } { 4 }$

D) $\frac { 1 } { 4 }$

E) $\frac { 5 } { 4 }$