An Efficiency Study of the Morning Shift at a Certain $f ( x ) = - x ^ { 3 } + 7 x ^ { 2 } - 3 x$

Multiple Choice

An efficiency study of the morning shift at a certain factory indicates that an average worker arriving on the job at 7:00 A.M.will have assembled $f ( x ) = - x ^ { 3 } + 7 x ^ { 2 } - 3 x$ transistor radios x hours later.Approximately how many radios will the worker assemble between 9:00 and 9:30 A.M.?

A) Approximately 7 radios
B) Approximately 13 radios
C) Approximately 14 radios
D) Approximately 390 radios