a)assume we have a cylinder ( with a top ) of height h and base radius r. if the top, bottom and wall costs per square meter are a, b and w dollars respectively, find the cost function K ( h, r, a, b, w )that gives the total material cost as a function of h, r, a, b, w

b)find all 5 partial derivative of the function K

how do i begin this question?

surface area= 2 (pi)rh + 2(Pi)r^2

top=a= (pi)r^2 bottom= b= (pi) r^2 wall=w=2(pi)r h

dk/dr= 2(pi)h + 4(pi)r

dk/dh= 2(pi)r

TC= a(dk/dr)+ b(dk/dr) + w(dk/dr)(dk/dh) ?

help please