When a Certain Commodity Is Sold for P Dollars Per $D ( p ) = \frac { 31,500 } { p }$

Multiple Choice

When a certain commodity is sold for p dollars per unit,consumers will buy $D ( p ) = \frac { 31,500 } { p }$ units per month.It is estimated that t months from now,the price of the commodity will be $p ( t ) = t ^ { 2 / 3 } + 5.15$ dollars per unit.The approximate rate at which the monthly demand will be changing with respect to time in 27 months is

A) -32 units per month
B) -35 units per month
C) -132 units per month
D) 35 units per month