Radioactive Decay of Atoms A and B

At time t = 0, a material is composed of two radioactive atoms A and B , where NA(0)=2NB(0). The decay constant of both kind of radioactive atoms is λ. However, A disintegrates to B and B disintegrates to C. Which of the following figuresrepresents the evolution of

NB(t)

NB(0)

with respect to time t ?
[NA(0)= Number of A atoms at t = 0]
[NB(0)= Number of B atoms at t = 0]