Volume of gold decreases by 12\(\%\),
= 88\(\%\) of 28 = 24.64
Volume of silver decreases by 14\(\%\),
= 86\(\%\) of 132 = 113.52
Volume of Iron ore increases by 6\(\%\),
= 106\(\%\) of 103 = 109.18
New volume = 109.18 + 149 + 113.52 + 75 + 24.64 = 471.34
Percentage decrease is given by,
\(=\frac{487-471.34}{487}\times100\)
\(=\frac{15.66}{487}\times100\)
\(=32\%\)
Hence, option D is the correct answer.The correct option is (D): Decrease of 3.2%