Need very urgent help with this question!

A unit mass is released with velocity v0(initial) = 0 of height h0(initial) = 200m. Assuming that the air resistance against the motion is fr = -0.1v.

a.) Write down the differential equation describing v(t) and solve it.

b.) Find the speed of the mass at the time it hits the ground.

Really reluctant to learn this as my final is soon! Thanks!