4. The table below shows the valuation of 2 buyers Bl and 82 for 2 different houses sold by sellers Sl and S2, where valuations a,b,c,d are non-negative integers. Assume you are following the procedure to find market clearing prices and you find that after you set all prices to zero, the preferred seller's graph does not have a perfect matching. Now you want to determine the minimum number of price-incrementing rounds required to find market clearing prices. Express the answer in terms of a,b,c,d using a single-line Python-like statement. Explain why your statement works for any set of non-negative integers [Hint: Consider using one or more of the following functions: sum(), long(), min(), max(), abs(), float(), into]. Valuation for Buyer SI'S house Bl B2 Valuation for S2's house d