Answer:
40g.
Step-by-step explanation:
Assuming that the solvent for thje drug is water, 4 liters of water equal 4000ml of water, and that has a mass of 4000 grams. Therefore, in order to get a 4% drug you need to add 40 grams of the drug (4000*0.01) and the rest is going to be water (3960 ml). The final product is going to consist on 40g of the drug + 3960ml of water.
