In a theater, the first row has 14 seats and each row has 3 more seats than previous row. If the last row has 50 seats, what is the total number of seats in the theater?	Answers:
A) 404  B) 408  C) 412  D) 416  E) 420
The number of seats in the theater is   14 + (14+3) + ...+ (14+36)=   13(14) + 3(1+2+...+12)=   13(14) + 3(12)(13)/2=   13(14+18) = 13(32) = 416   The answer is 416.
<result>D</result>
In a theater, the first row has 14 seats and each row has 3 more seats than previous row. If the last row has 50 seats, what is the total number of seats in the theater?