The maximum profit is the highest point on the curve at (3, 45), and since the y-value is the profit in hundreds of dollars, the maximum profit is $4500.
The shop is making a profit as long as the curve is above the x-axis, so this is over the given interval (0, 10).
The maximum profit is earned at x = 3, and the x-value is the money spent on advertising in hundreds of dollars, so this means that $300 was spent of advertising.
There is a 3% chance of each light bulb being defective, and we only want 5 of them to be defective. The chance is then:

Or this really small number: 1.13474853e-8
My only guess is a^2 + b^2 = c^2