Simplify the Expression $( \sqrt { 6 } - 3 ) ( \sqrt { 7 } - 5 )$

Multiple Choice

Simplify the expression. Assume all variables represent positive real numbers.
- $( \sqrt { 6 } - 3 ) ( \sqrt { 7 } - 5 )$

A) $- 7 \sqrt { 42 } + 15$
B) $\sqrt { 42 } + 15$
C) $\sqrt { 42 } - 8 \sqrt { 7 } + 15$
D) $\sqrt { 42 } - 5 \sqrt { 6 } - 3 \sqrt { 7 } + 15$