How do you solve for k when there is a +C?

Write and find the general solution of the differential equation that models the verbal statement. The rate of change of / is proportional to /. (Use k for the proportionality constant.) dNV = KN dt N(t) = At + C e Evaluate the solution at the specified value of the independent variable. When t = 0, N = 350, and when t = 1, / = 400. What is the value of / when t = 4? N(4) =