The net cost equivalent is the price the customer pays after deducting all the discounts. To find the net cost equivalent given an amount n of discounts, we use the following formula
[tex]N=(1-d_1)(1-d_2)\ldots(1-d_n)[/tex]Where d is the discount written as a decimal.
In our problem, we have a series discount of 20/10/10/20, therefore, the net cost equivalent is
[tex]\begin{gathered} N=(1-0.20)(1-0.10)(1-0.10)(1-0.20) \\ =(0.8)(0.9)(0.9)(0.8) \\ =0.5184 \end{gathered}[/tex]