Solve the Problem $\mathrm { d } = \sqrt { \mathrm { L } ^ { 2 } + \mathrm { W } ^ { 2 } + \mathrm { H } ^ { 2 } }$

Solve the problem.
-A formula for the length of a diagonal from the upper corner of a box to the opposite lower corner is $\mathrm { d } = \sqrt { \mathrm { L } ^ { 2 } + \mathrm { W } ^ { 2 } + \mathrm { H } ^ { 2 } }$ , where $\mathrm { L } , \mathrm { W }$ , and $\mathrm { H }$ are the length, width, and height, respectively. Find the length of the diagonal of the box if the length is 23 inches, width is 15 inches, and height is 7 inches. Leave your answer in simplified radical form.

A) $3 \sqrt { 5 } \mathrm { in }$ .
B) $\sqrt { 803 } \mathrm { in. }$
C) $\sqrt { 1606 } \mathrm { in. }$
D) $3 \sqrt { 10 } \mathrm { in }$ .