Did Megan McArdle Really Graduate from a Business School?

She writes:

On Comparing Tax Cuts to Social Security: the only reason the [CBPP's two:] numbers [valuing the size of the upper-income tax cuts and the Social Security deficit:] looked even remotely the same size was that they were using a present value...

Did this person really graduate from a business school?

Either she needs her tuition back because they did not teach her what present value is for, or the business school needs to revoke her degree to get its reputation back...