What happen if in the wage instead of 10 and 11 we take D with 9.9 and November with 9?

Let the working hours in November be \(10\)
So, working hours in December will be \(9\)

Let the wage in November be \(9\)
So, the wage in December will be \(9.9\)

Col. A: \((10)(9) = 90\)
Col. B: \((9)(9.9) = 89.1\)

Col. A > Col. B

Let us solve it with a different approach

Let the working hours in November be \(x\)
So, working hours in December will be \(0.9x\)

Let the wage in November be \(y\)
So, the wage in December will be \(1.1y\)

Col. A: (\(x\))(\(y\)) = \(1xy\)
Col. B: (\(0.9x\))(\(1.1y\)) = \(0.99xy\)

Dividing both sides with \(xy\);

Col. A: \(1\)
Col. B: \(0.99\)

Again, Col. A > Col. B

Hence, option A