a cup of Rice (raw) weighs 7 oz

Question

One cup will serve 4 people. Rice is purchased in 2 pound boxes for $1.99. How much would the rice cost if you were serving 20 people? 

Answer 1

A cup is a unit of volume. A pound is a measure of weight.
This is a poorly written word problem.
You wold need 5 cups of rice (20 ÷ 4).

The writer assumes that 1 cup = 1/5 pound. Not true.

So going along with the writer,

You need two boxes for a cost of $3.98