The Thoroughbred Bus Company Finds That Its Monthly Costs for One

Multiple Choice

The Thoroughbred Bus Company finds that its monthly costs for one particular year were given by $C ( t ) = 100 + t ^ { 2 }$ dollars after t months. After t months, the company had $P ( t ) = 1,000 + t ^ { 2 }$ passengers per month. How fast was its cost per passenger changing after 4 months Round your answer to the nearest cent.

A) $0.29 per month
B) $0.01 per month
C) -$0.21 per month
D) $0.46 per month
E) $0.07 per month