If the average (arithmetic mean) of the four numbers 5, 15, 30, and (N + 1) is 30, then N =	Choose the correct choice from the following answers:
A) 19
B) 20
C) 69
D) 78
E) 292
5+15+30+N+1= 30x 4 = 120   =&gt;N +51 = 120   =&gt;N=69   Answer 69
<result>C</result>
If the average (arithmetic mean) of the four numbers 5, 15, 30, and (N + 1) is 30, then N =