Explanation:

Applied shares=10000                         On application Rs3; on allotment Rs2; on first call Rs4 and on final call Rs1 per share.

alloted shares=4,000

prorata shares= 6,000                                                                  (10000-4000) (excess apllication received)

Excess money received = 6000 * 3 = Rs.18,000

Allotment money due - 4000 * 2 = Rs. 8,000

So amount due on allotment adjusted against excess amoney. so no allotment money is required to be received

Excess money = 18000- 8000 ( used for allotment)              

(NOTE: there is no excess amount on pro-rata rather surplus generated will be refunded)