Let T(r)=5r3−2r denote the temperature, in degrees Celsius, on the surface of an expanding metal sphere whose radius r is measured in centimeters. When r=2 cm the radius is increasing at a rate of 0.1 cm/min. What is dtdT, in degrees Celsius per minute, at that instant?
a) 58
b) 5.8
c) 4.1
d) −5.8