Selenium from 0.108 g of Brazil nuts was converted into a fluorescent product, which was extracted into 10.0 mL of cyclohexane. Then 2.00 mL of the cyclohexane solution were placed in a cuvet for fluorescence measurements.

Question

Selenium from 0.108 g of Brazil nuts was converted into a fluorescent product, which was extracted into 10.0 mL of cyclohexane.  Then 2.00 mL of the cyclohexane solution were placed in a cuvet for fluorescence measurements.

A.) Standard additions of fluorescent product containing 1.4ug Se/mL are given in a table:

Volume of standard added (uL):
0, 10, 20 , 30 40

Fluorescence intensity:
41,4, 49.2, 56.4, 63.8, 70.3

What is the weight % of Se in the nuts?

I made a graph from the values to get a line y = 0.724x + 41.74. Setting y = 0, x = 57.65

I'm not sure what's the next step in solving this.