The carton consists of a rectangular prism, and its volume is given by the formula:

Where V is the volume, L is the length, W is the width and H is the height.
Using L = 1 2/3 = 1.666 ft, W = 1 2/5 = 1.4 ft and H = 1 1/2 = 1.5 ft, we have that:

So the volume of the carton is 3.5 ft^3
You can also use the numbers in their fraction form:
L = 1 2/3 = 5/3
W = 1 2/5 = 7/5
H = 1 1/2 = 3/2
