A tank with rectangular base and rectangular sides, open at the top is to be constructed so that its depth is 2 m and volume is `8 m^3`. If building of tank costs Rs 70 per square metre for the base and Rs 45 per square metre for sides, what is the cost of least expensive tank?

Explanation

The volume of the tank is

`2xym^3=8`

`2xy=8`

`impliesxy=4`

`impliesy=4/x`

Base area=`xy=x(4/x)=4m^2`

Area of four sides=`2xx2(x+y)=4(x+4/x)`

Let C be the total cost

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