Solving Force vs Time Graph Homework Problem

[jeya]

Homework Statement

A rocket increase its upward Force uniformly from 5*10^6N to 8*10^6 Nover 15s

find the impulse?

Homework Equations

Impulse?

The Attempt at a Solution

My answer=(5*10^6 +8*10^6/2)15=9.75*10^7N.s

Book answer=6*10^7

please help me how to find the right answer?

 

[PhanthomJay]

What is the question? (You forgot to include it)