Help Calculus? Find the velocity

The acceleration function (in m/s^2) and initial velocity for a particle moving along a line is given by

a(t)=−20t−30
v(0)=40
0 < or equal to t < or equal to 3

(a) Find the velocity (in m/s) of the particle at time t.

Thank you. Please explain as best as possible.

v(t) = INT {a(t)} dt
v(t) = INT {-20t - 30} dt
v(t) = -10t^2 - 30t + C

Now use v(0) = 40 to find C.

v(0) = 40 = -10*0^2 - 30*0 + C
C = 40

v(t) = -10t^2 - 30t + 40