divide the price of the olive oil by the volume of the olive oil to find the price per ounce. 5.88/25oz=0.2352 dollars/ounce. Then you have to multiply the volume of the bottle by .60 to find what 60% of the volume is.
0.60x25=15 ounces. since in the first two weeks she used 15 ounces which has a price of 0.2352 dollars/ounce you have to multiply 15 by 0.2352 which equals 3.528 dollars.