An organization offers only three types of memberships. Basic memberships cost 50$ each, standard memberships cost 70$ each, and premium membership costs 100$ each. Last year, a total of 200 memberships were purchased at an average cost of 80$ per membership.

Which of the following statements **individually** provide(s) sufficient additional information to determine the number of premium memberships purchased last year?

Indicate **all** such statements

- Last year, the number of basic memberships purchased was equal to the number of standard memberships
- Last year, the number of premium memberships purchased was twice the number of basic memberships
- Last year, the number of annual memberships purchased was 100 for one of the three types of annual memberships

**My approach**

From the given info we have 2 equations,

- (50.Nb)+(70.Ns)+(100.Np) = 80(200)
- Nb+Ns+Np = 200

So, options A, B are sufficient by themselves because they give us the third equation to solve the simultaneous linear equations.

What about option C? It canâ€™t be sufficient by itself right?