A certain type of fern has been shown to effectively extract arsenic from soils. In one experiment, the ferns (containing 5 ppm arsenic) were grown for two weeks in normal soil which originally contained 6 ppm arsenic. After the 2 weeks, the arsenic in the soil dropped to 5 ppm and the ferns were analyzed and found to contain 755ppm of arsenic. What is the ratio of soil mass to plant mass?