$2.$ A sub$-$contractor company you work for requires a concrete mixer for your construction firm as the one you currently use has reached the end of its life cycle. A plant hiring company has a second$-$hand concrete mixer for sale, which is still in good working order. Your company thus purchases the second$-$hand concrete mixing truck, which can carry approximately $18000$ kg of concrete, for R$273000\mathrm{.}2\mathrm{.}1$ What will the book value of the concrete mixer be after three years if the rate of depreciation is $18\%$ per annum, using:a$)$ the straight$-$line method $(3)$b$)$ the reducing balance method $(3)$