The cuboid shape hall is 40m long, 15m wide and 3m high. The walls and ceiling needs to be painted. A 10 litre tin of paint covers 25m2 and cost is £10. What is the total cost of paint?

Option A.

Step-by-step explanation:

The lines that we have is:

y = (1/2)x - 3

y = -2x + 16

Now, two lines of the shape y1 = a1*x + b1 and y2 = a2*x + b2 are parallel if both lines have the same slope, this means that a1 = a2.

Those lines are perpendicular if a1 = -1/a2

now, the slope in the first equation is (1/2) and in the second equation is -2.

so a1 = 1/2

-1/a1 = -(2) = a2

so the two lines are perpendicular, the correct option is A