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Under favorable weather conditions, the management of Flesher Farms expects its raspberry crop to have a $120,000 market value. An unprotected crop subject to frost has an expected market value of $80,000. If Flesher protects the raspberries against frost, the market value of the crop is still expected to be $120,000 under frost-free conditions and $180,000 if a frost occurs. What must be the probability of a frost for Flesher to be indifferent to spending $20,000 for tents to provide frost protection?