Perform the Operation and Write the Result in Standard Form $( \sqrt { 19 } + \sqrt { 8 } i ) ( \sqrt { 19 } - \sqrt { 8 } i )$

Perform the operation and write the result in standard form.​ $( \sqrt { 19 } + \sqrt { 8 } i ) ( \sqrt { 19 } - \sqrt { 8 } i )$ ​

A) 31
B) 27
C) 28
D) 29
E) 30