Shorten the credit period and charge fees.

To change the credit policy relative to the original policy:

(1) Benefit increase = 100*30%*20%=6 (ten thousand yuan)

(2) Under the 30-day credit period, the accrued interest of accounts receivable = (100/360) * 45 * (1-20%) *10% =1(ten thousand yuan),

Cash withdrawal period after changing credit policy = 10*50%+50*50%=30 (days),

After changing the credit policy, the accrued interest of accounts receivable = [100 * (1+30%)/360] * 30 * (1-20%) *10% = 0.8667 (ten thousand yuan).

Accrued interest increase = 1-0.8667=0. 1333 (ten thousand yuan);

(3) Increased collection fee = 5000-8000 =-3000 (RMB) =-3 (RMB ten thousand),

Bad debt loss increase =100 (1+30%) *10%-100 * 6% = 7 (ten thousand yuan),

(4) Cost increase of cash discount = new sales level * new cash discount rate * proportion of customers enjoying cash discount-old sales level * old cash discount rate * proportion of customers enjoying cash discount =100 (1+30%) * 2% * 50%-100 * 0.

Pre-tax profit and loss of changing credit policy = income increase-cost increase = 6-(0.1333-3+7+1.3) = 0.5667 (ten thousand yuan),

Since the increase in income is greater than the increase in cost, the credit policy should be changed.