Let us start with qty A

The initial sales could be anything let us suppose that it was \(1000 units\) now the new sales after reduction in sales force would be \(500\)

Therefore percent decrease would be \(50%\)

However it could be the case that initially the sales was only \(10000\) and the new sales would be \(9500\) after reduction of \(500 units\).

% decrease would be \(\frac{500}{10000} * 100 = 5%\) approx

Now coming to Qty B it is fixed at \(15%\)

Hence we cannot definately conclude either A or B is the ans hence

D
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This is my response to the question and may be incorrect. Feel free to rectify any mistakes