Integration Homework Help

MillerL7
A population of cattle is increasing at a rate of 200 + 10t per year, where t is measured in years. By how much does the population increase between the 4th and 6th years. What is the total increase?

I tried using integration, and have b=6 and a=4, with interval of 2, but it was wrong. Please help me. Thank you!

$$P(t) = \int (200+10t)dt = 200t+ 5t^2$$
$$P(6)-P(4)=?$$