query in Sec.23(1)(c)

In Sec.23(1)(c), it is provided that in case the actual rent recieved (ARR)is less than the expected rent (ER) "owing to vacancy", then ARR shall be taken as annual value.
but i want to know if the ARR is already less than ER even if rent of vacancy period is to be included in the ARR, then what value is to be taken.
V.K. Singhnia points out that in the latter case, the ER should be taken but the loss due to vacancy shall be deducted from that amount.
for instance..............

ARR (6000x10) = 60000
ER = 75000

Rent of vacancy period (2 mnths) = 12000

even if Rs.12000 is added to ARR,
then also it comes out to be Rs.72000 which is in itself less than ER.

that means the vacancy period hasn't had any effect on the ER.
which value to be taken?
as per V.K. Singhania, the Annual value will be Rs.63000 [75000-12000(loss of vacancy)].
Sec.23(1) (c) doesn't provide for the deduction of any loss of vacancy..
kud u pls clear the above point....

Even circular no.14/2001 which is in this regard kud not be of help....