1. \text{Convert percentages to decimals: }
20\% = 0.20
2. \text{Multiply the decimal values of the independent variables:}
0.20 \times 0.20 \times 0.20 = 0.008
3. \text{Convert the decimal result back to a percentage:}
0.008 \times 100 = 0.8\%
\text{Hence, the percentage of success necessarily is 0.8\%.}