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If the house was titled in your father's name alone then the cost basis for determining gain or loss on the sale is the fair market value on his date of death. So if the fair market value on his date of death was $45,000 and it was sold for $28,500 then there is a loss of $16,500 not a gain so you will not have to pay tax on any gain.
If your father was a resident of MO then there will be no estate taxes imposed.