Why should investors watch the performance of stock indexes over an extended period of time rather than reacting to daily increases or decreases?

On december 31, 2016, the decarreau, andrew, and bui partnership had the following fiscal year-end balance sheet: cash $10,000accounts receivable $20,000inventory $25,000plant assets - net $30,000loan to decarreau $18,000total assets $103,000accounts payable $14,000loan from bui $15,000decarreaua, capital (20%) $32,000andrew, capital (10%) $23,000bui, capital (70%) $19,000total liab./equity $103,000the percentages shown are the residual profit and loss sharing ratios. the partners dissolved the partnership on january 1, 2017, and began the liquidation process. during july the following events occurred: * receivables of $18,000 were collected.* all inventory was sold for $15,000.*all available cash was distributed on january 31, except for$8,000 that was set aside for contingent expenses.the book value of the partnership equity (i.e., total equity of the partners) on december 31, 2016 isa. $58,000b. $71,000c. $66,000d. $81,000