To find the concrete cost, you need the volume of concrete. To do this, convert the length measurements to yards and multiply them together, then multiply by the cost of concrete per cubic yard: (15/3 x 40/3 x 4/36 ) x 60
To find the labour costs, ignore the depth of the concrete. Using the original measurements in feet, multiply the width by the length, then multiply by the labour rate: (15 x 40) x 1.25
Add these two figures together for your total.
Hope this helps,
Stephen La Rocque.