[填空题]
A food company produces ice creamsd4(pk ( fn):lvf 4bmbjv9ck5a lr lsf0 dl+)/y in the shape vc2 ax*y.o)fyg7 2 g-faaprh:of a cone with a hemisphere on top. Each ice cre 7f-2 xg*fyvgaa2cyao)rp: h.am consists of a cone base with height h and radius r, and a hemisphere on top of the cone's base, also with a radius of r. The total surface area of the ice cream cone is in cm$^2$ and is given by the formula
A=2$\pi$$r^2$+$\frac{60\pi}{r}$,
where r is the radius of the cone, in cm.
The ice cream designers of the company have been instructed to minimize the surface area of the cone in order to reduce the melting rate of ice cream.
1.Find $\frac{dA}{dr}$=a$\pi$r - $\frac{b\pi}{r^2}$.
a= , b= .
2.Calculate the value of r that minimizes the total surface area of the ice cream cone.
r= cm.
