Question 1070878
The area is,
{{{A=pi*(R[2]^2-R[1]^2)}}}
{{{A=pi*(11^2-4^2)}}}
{{{A=pi*(121-16)}}}
{{{A=105*pi}}}{{{m^2}}}
The cost would be,
{{{C=105pi*21}}}
Work that out for a final answer.