Inventory problem

please work out my problems:

the cost of verification inventory valu is on 24th march,07 was 400000.goods are sold at a profit of 25% on cost.on 21st march,goods on the sale value of 100000 were sent on sale or return basis to a customer,the period of approval being two weeks.he approved 80% of the goods on 31st march.the cost of inventory as per books is ---

a).480000                                                                                                                                                                  b).416000

c).428000                                                                                                                                                                   d).none of these.