Add or Subtract $\sqrt { 50 } - 6 \sqrt { 162 } + 7 \sqrt { 128 }$

Multiple Choice

Add or subtract. Assume all variables represent positive real numbers.
- $\sqrt { 50 } - 6 \sqrt { 162 } + 7 \sqrt { 128 }$

A) $- 7 \sqrt { 2 }$
B) $- 53 \sqrt { 2 }$
C) $7 \sqrt { 2 }$
D) $- 162 \sqrt { 2 }$