Mix of two ads types Question still unanswered

Ads in the boring business magazine are read by 300 lawyers and 1,000 M.B.A.s. Ads in the consumer publication are read by 250 lawyers and 300 M.B.A.s. If Harry had \$4,200 to spend on advertising, if the price of ads in the boring business magazine were \$700, and if the price of ads in the consumer magazine were \$350, then the combinations of recent M.B.A.s and lawyers with hot tubs whom he could reach with his advertising budget would be represented by the integer values along a line segment that runs between the two points

a.
(3, 600, 0) and (0, 7, 200).

b.
(3, 000, 3, 600) and (1, 800, 6, 000).

c.
(0, 3, 600) and (1, 800, 0).

d.
(3, 600, 4, 200) and (1, 800, 7, 200).

e.
(2, 400, 0) and (0, 6, 000).

My attempt was to find a budget line which is $700b+350c=4200$, where b stand for business magazines and c for consumer ones. But i do not know how this would translate into the answers that are given.
Here is my method, which is less rigorous but perhaps quicker, and I believe allows you to see the answer more easily, at least in this case. It may not be true in every case.

Since the line segment will represent all combination of lawyers and M.B.A's that we can reach, it must include the extremes. That is, it must include the cases where we maximize the number of lawyers that we reach, and when we maximize the number of M.B.A's that we reach. In fact, these will be the endpoints (since if we are not maximizing one of these we have to be somewhere in-between). Because of this we can do the following:

1) Figure out how many lawyers we can reach, if we focus on only reaching lawyers. Well, the business magazine lets me reach $300$ lawyers for every $\$700$ I spend. The consumer magazine lets me reach $250$ lawyers for every $\$350$ I spend or equivalently $500$ lawyers for every $\$700$ I spend. This is important because we are comparing $\$700$ worth of one magazine to $\$700$ worth of another: we are making a $1:1$ comparison, which is necessary.

What the above paragraph tells us is that, if I want to reach as many lawyers as possible, I should spend all my money on the consumer magazine ($500&gt;300$). With a budget of $\$4200$ I can buy $4200/350 = 12$ ads. $12$ ads lets me reach $12*250 = 3000$ layers. So the most lawyers I can reach is $3000$. Additionally, $12$ consumer ads lets me reach $12*300=3600$ M.B.A's, hence one point (one extreme) is 
$$
(3000,3600)
$$

To get the other point, find out how you can reach the most M.B.A's.

One thing to note: The fact that things like $(0,3,600)$ are options should perhaps prompt you to consider maximizing the lawyers reached and maximizing the number of M.B.A's reached (since a $0$ indicates reaching none of one group). Not that doing so will be correct, but if you are stuck such a hint might lead you to the correct answer.

Cheers.